A number of questions regarding final touches to audio system/digital/plex

My current stereo is only an amp, turntable speakers. (McIntosh, PSB). I’m looking to add digital. I have a laptop running plex with an external with about 500gb of FLAC files. I also have a tidal account. I chose the PS Audio Nuwave for my DAC and I’m looking forward to hooking it up. I have a number of questions regarding final touches on this system and any help would be much appreciated..so here goes:

Here is the equipment I have available to me to play the digital files: Xbox One, PC, Smart TV

I read that using optical out bypasses the internal DAC so I’m wondering if it matters if I use the XBOX one or Smart TV and run optical?

If I use the PC, I could run the PLEX app on the same computer as the PLEX media server. When I’ve done this in the past, I’ve actually watched it buffer, meaning it still runs through the network even though it’s locally stored. I find that to be counter-intuitive but most importantly, is that "worse" from an audio/jitter perspective than playing the music through a local media player on the pc? Roon seems nice..but I’d rather invest my money in hardware than consolidation software.

Is there anything I’m missing here? Is there a cap on the size of the music file when it runs through the network? Loss of fidelity, etc..

Bottom Line..If this is what you had, what would you do in terms of setup. Or would a small investment produce significantly greater results?

Interconnects: I know nothing about quality ones. I'm new to this and I could use some help. I really don't want to spend a fortune but I want to make sure my interconnects aren't making my systems worse. I would basically need rca to rca, optical to optical, rca to 3.5, and usb to usb type 2.

Power conditioners: I’m seeing rotel, Furman and APG’s for around $100 on ebay. I’d prefer to stick to this budget but I’ll go over that if I’m getting junk for that pricing. I’ve read some people say that there’s audio degradation if it’s on the lower end. I’d accept less benefit..but not specific degradation. Running a separate line isn’t an option right now so any thoughts on brand, model, cost basis would be appreciated.

After all of this is done, I’ll look into room treatments and I think I’ll be "done"..that is until the next itch.
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Use the PC. If your music files are stored on the same computer, just use a regular music player. Try Clementine or Foobar. Both are free music players that should do anything you need. If you use Plex for other things, just leave it setup the way it is.

For cables, just go to Best Buy. They sell Audioquest. Get some entry level cables for whatever you need. They won't be expensive and you'll never have to worry about quality.

For power, get whatever your $100 or so budget will get you from either Furman or Monster. You'll be fine either way.

+1 mgreen.
I just found foobar and it is a great free app. 
If you want to aid in sound reproduction, I suggest getting Fidelizer and buying the Pro version. It reallocates windows system to prioritize audio. I never thought it would do as much as it did to my system. Everything sounds 'alive' compared to not using it.
YMMV, but it is worth looking at.
@gdnrbob -very cool. I'll check it out