You are not going to be able to use a PC to emulate the cable box. All you will be able to do is use it for streaming apps, and if so, ensure you are either in a place where they don't bill for data overages, (1.25tb), or you may have to sign up for unlimited data (49$), because streaming can use a whole lotta data. Your average 4K data stream can use over 8gb per hr. Your standard HD stream can use as much as 2 to 3 GB per hr. Compressed streams lower that quite a bit, but remember a compressed stream is a lossy stream so you will lose some resolution.
I use PLEX, and have a server setup with all my DVD's on it, plex subscription also includes live tv, and any device that can run plex software, computer. most tv's, firestick, laptop/desktop/tablet/cell phone etc etc, can access the plex system and stream from it, even outside the home.
Probably any PC with an HDMI out will be good enough. I happen to use a fairly high-powered PC with RTX 3060 Ti video card to watch fullscreen on a 720p 10" secondary monitor in Firefox while I use my PC for other things. I use Autohotkey to send keyboard shortcuts to the unfocused Firefox window, and it allows me to do things like implement skips of various lengths (e.g. Win+Ctrl+Alt+Right Arrow to skip 2.5 minutes), like I did in YouTube TV. I can also use a remote control when the window is focused, but explaining that would really get into the weeds. The problem is that only playback can be controlled this way. To use the guide, select from the DVR list, etc, you need a keyboard/mouse, not really friendly to sitting on your sofa.
While watching in a browser has a number of advantages important to me, it's not a great experience in general. Cox's Cloud DVR (rebranded Xfinity, actually) is problematic in browsers:
Skips can rarely hang or more commonly incur a 10-20 second delay without doing anything. It mostly works, though.
To watch an in-progress recording, I can't let my watch point get within a couple minutes of the current "end" of the recording, i.e. the "live point", lest it rebuffer every minute or so. It's not smart enough to allow for the necessary buffer.
Watching Live TV is pure streaming, with no pausing the program, skipping back, etc. If you want to do that, you need a Cox box. Worse, for news channels like CNN (and probably all all channels) , Live TV quality is WORSE than DVR recordings. The scrolling text at the bottom is lower res and stutters a bit, and there is judder for all motion, even the limited movements of the news anchors sitting at their desks. This doesn't happen with DVR recordings.
Those shortcomings aside, at least there aren't any micro audio dropouts like I observed on my iPad, which caused me to give up on that a few months ago and go back to using my PC and monitor, which I'd used with YouTube TV the last 5 years. Those dropouts are really noticeable when using headphones as I normally do. Also, using a single keypress is a lot better than tapping a bunch of times on an iPad to get the thing to skip over a commercial block!