Reddit mentions of 2pcs 9.53.52.5cm 4 Way Nail File Art Shiner Polish Buffer Buffing Block Design Trim

Ok, here we go.

The Bridge: Looks OK to me, but i replaced the saddles (roller saddles) and the trem block on my Pacifica because of preference. You can remove and disassemble the bridge and clean everything (steel wool and vinegar work well) or leave it and it will be fine.

The Nut: It should not drastically alter the action, because any nut you have on your axe should be filed to the exact height that is ideal for your setup. Tusq, bone, roller nuts, etc are all fine and well but IME, a properly filed, smoothed and lubed plastic nut has not hindered my tuning stability at all. YMMV.

The Frets: The edges look ok to me but if you want to shape them a bit more you need a (preferably) 3 sided file. Be very careful and move very slowly as to not cause damage. As for polishing the frets, you can use steel wool (Tape your pups!) or very fine grit sandpaper carefully. I personally have found that a fingernail buffer (like https://www.amazon.com/dp/B00X68IVGS/ref=sspa_mw_detail_6?psc=1)
works best for me. Can find those anywhere you go. I've also seen techs use pencil erasers to polish frets.

The Fretboard: If a fretboard gets too dry, it will shrink and will cause fret sprout. I don't recommend lemon oil (some do) but prefer either mineral oil or the Dunlop Fingerboard Oil. Don't overdo it, once a year or twice if its really dry is all you need. Over oiling is just as bad as it being too dry.

Pickups: I personally (some may hate me for this) dont believe pickup swaps make any improvement on your sound that an EQ pedal can not. Plus, an EQ pedal has many more uses and is quite versatile. That said, do what makes you happy so you love your sound, but always take a look at your amp first.

Pickguard: Replacement pickguards almost never line up to the existing holes. It is what it is, just drill small pilot holes before adding the screws.

Sanding: Yes, i think 100 is too course and youll end up removing more material than you should. I use 220/320 followed by 600 and lastly 1000. This is also subjective but IME, 100 will create uneven spots and headaches.

All in all, the best advice is to get as many different opinions as you can as everyone has different techniques and ways of doing things. Get all the opinions you can and find which ones make the most sense to you for your specific project and end goal. Also, have fun.