I just got a new Mac mini M1 and was wondering if it would be better as server than my QNAP NAS.
And would it be better to use a usb drive such a a Samsung T7 or use nas for files I have a 10 gig ethernet connection to the nas on my Mac.
Well...you would need to prove far more information in order to compare.
What specific brand /model and hardware specs is the NAS?
What specific Mac mini M1 do you have?
I am not familiar with the M1 hardware, but assume it has same product tier of different power cpu etc.
You should try it. 10gbe from the mini to the NAS is faster than usb3. How much improvement you will see is not known without more information, but it will be faster.
M1 Mac mini is the best server hardware that exists right now.
QNAP NAS TVS-EC1080. Intel® Xeon® E3-1245 v3 3.4 GHz Quad Core Processor
32 GB Mem.
Mac mini M1 8gig mem
So you running without hardware transcode now. Can't say Channels-DVR is set up to do hardware transcode on an M1, but its going to be faster regardless. I have seen Plex forums where user was using an M1 and doing 2 4k transcodes + 6 1080p transcodes all simultaneously. I think these were only around 2mbit each, but the quantity going at the same time is still impressive.
What else are you using the Mac Mini for? If it is going to be lights off dedicated, then I'd definitely pick that over the QNAP NAS for the server. But I would probably get a dedicated external USB drive... they are so cheap... rather than adding complexity and going over the network for the drive. Dollar for dollar, I think a Mac Mini is going to kill any NAS at this, at way less cost. Just my opinion, and I'm running Channels on a 9 year old i5 Mac Mini when I have two QNAP NAS boxes that I could have used.
But if the Mac Mini you have is going to be used as a desktop computer for other things, not sure I'd want a DVR running on it too. The main thing with the DVR that it be available and uninterrupted.
^^^ This. I first used my 2018 Mac Mini as my DVR but I also used it as my primary desktop. Doing this I was constantly interrupting the DVR or the DVR would interrupt me from doing something. That is why I moved it to my NAS. I still want the DVR on my Mac Mini...I'm debating buying a MBA as my primary and letting my Mac Mini be my server for all things.
My preference is a NAS since after setup it's hands off and you can forget about it. My DS720+ handles 4 ATV's and all recording needs. My two Mac Minis are in use as desktops.
The Mac Mini I'm using is more hands free than my NAS boxes. It autoboots and logs in if it gets turned off and it has no display, keyboard, or mouse. It just works. My NAS boxes have been fraught with maintenance issues and malware attacks over the last year and if you do have to do an update its extended down time to reboot first and after. So its all in how you use this stuff.
This is kind of why I want to move the mac mini to a dedicated server and use my NAS as a backup solution. Sure the NAS works and it does a great job...I just feel like its more prone to attacks.
Yes the Minis are also a good choice for hands off that's why I gave my wife one and she does not like change or complications. My Synology it's been very good to me so I can't complain but I did start with an iMac then went to a windows 10 box but no hardware transcoding. Ended up getting the DS720+ with no regrets.
A Raspberry Pi 4 makes a great Channels DVR server. Extreme low maintenance, since it is only the channels custom image on it. Updates are fast and easy.
I have 2 of them. One for each user, since Channels does not support separate user profiles.
It is a low power, always on device, I do have them in a case with a small fan to keep it cool. But have had no issues with them. I like them as dedicated "appliance" type network device thats only job is to be a Channels DVR and never realy need to touch the thing after it is setup,
Before, i had one sever hosted on my Intel NUC running Linux Mint, but I also used that system for many other things and it was difficult when i needed to reboot or update that OS it taking down or interfering with the DVR.
The only downside to Pi 4 DVR is that it is not a hardware power house. Just powerful enough for 1x remote transcode stream, and takes longer for comskip to process, due to its lower powered CPU, but it is plenty sufficient for single users like me.
And i'm quite sure, that the next gen, the Pi 5, will be even more powerful and desired as a Channels DVR server...
I would never spend ~$900 on a Mac Mini M1....just to only use it for a Channels DVR....its your money to burn though.
I just set up a Mac Mini M1 last week as my server. It's the best decision I've made. Everything runs so smoothly. Going between channels is so quick. Commercial detection is very fast if that is important to you. I don't know much about the NAS you have but the Mac Mini is amazing as a server.
A Mac Mini is cheaper than most Intel based NAS boxes with decent horsepower. And in my case, My Mac Mini is 9 years old and was occupying a box in the closet when I tasked it with this duty! 
Mac's run always like the day you bought it add a SSD and some memory and you get new life.
Well, the Intel NUC i have is an i7 Quad 3.5ghz and cost only $400 few years ago...and came with 32gb ram.
Also, looking on Ebay, you can find many high end NUCs, or other mini form factor computers, with plenty of cpu power, for very cheap. And u can easy make it a NAS by installing a large TB ssd, or use a usb 3.0 multi bay dock, or thunderbolt hdd bay.
Apple hardware is way overpriced for what you get. But if it makes you feel better seeing the shiny Apple logo on it....have fun.
My NAS has many jobs. By day it's DVR server and runs some Docker images backs ups all our photos from our smartphones. At night it's a backup server for our Mac's. It can handle all without a hitch or intervention. Plenty of bandwidth with two giga network ports bonded and straight to the router.
A MacMini seems over kill for a channels DVR server. A cheap Windows mini PC with Intel Quicksync is more than enough. I can get one for under $200 Dollars with Windows 10 Pro installed.
No doubt its probably overkill, but the M1 is probably the fastest option. And I can't complain that my $599 i5 Mini that I bought NINE years ago still runs great and kills at at DVR duties.