I have an HD Homerun Prime Plex and Channels. On my Roku Ultra 3 nights ago I watched Live TV on Channels. There is no commercial skipping. There are no actual settings it is an early beta app. I am set not to transcode so full resolution through Channels.
Before I started using Channels I used to watch all of my live TV on Plex through the HDHomerun Prime because my cable dvr was fubar. I can pause ff/rwd. I also recorded all my shows direct so full resolution mpeg2 with both 5.1, 2.0 AC3 audio & sub titles in a .TS rapper.
In the Plex settings you check a box to allow for mpeg2 playback.
I do not have experience with OTA & Channels, but many Plex users use OTA exclusively. I plan on adding an OTA tuner this year for my local and PBS stations. You just can't beat OTA for pure picture quality. I have my aerial on my roof from 1970 and upgraded it years ago with RG6 which goes directly to my TV so every once in a while I check out the news or something on it just because.
If you're happy with your ATV's I won't knock them. My major gripe about them compared to my Rokus is that I have an extensive blue ray collection. It took a long time to rip them in pure uncompressed form with their DTS and Dolby 7.1 tracks and now DTS-X and Dolby Atmos and ATV's just weren't compatible with so many formats of audio and video for years.
Now I'm not talking about a Roku Stick or a Roku TV. However when I installed a TCL 55" 4K and soundbar system for my parents a few years ago the first thing I did was playback the One 4K BD I had over Plex on that TV. Blade Runner the final cut. The TV immediately recognized the Dolby Vision and Atmos. At that time it would have been impossible for an ATV to play it back without remuxing the audio and not passing the Dolby Vision.
There are several other reasons that I like Roku's over the plethora of devices on the market. I'll just tell you one. Long before Roku even put a Netflix button on there own remote I was programming Direct to Service Buttons (i.e. any favorite you had on your home screen I could make a custom button for it) on custom remotes and integration/automation systems long before we are where we are now with Home Automation.
I have an Nvidia Shield TV I use now for everything, but I had hip replacement surgery 5 weeks ago and my shield was downstairs with me the first 4 weeks. I haven't had a chance to set the Shield back up yet that'll be tomorrow.
I do not understand how you can claim mpeg2 does not work when I have proof that it does.
I do not know if it is coding or hardware toggle in Plex I just know for sure that I am able to watch mpeg2 in live or recorded form on my Roku Ultra...
I apologize for my tone or flamyness I've been in lot of pain lately living on minimal or no sleep ending up with screeds here and there!