Best underwear?

All the pads have sticky tape on one side and easily fit inside boxer shorts. No problem with washing the shorts after you use the pads.

Yes, I'll second that: both regular and boxer briefs work fine. Loose boxers might not work, because the pad might not be snug.

I went and bought a big bag of "depends" before my RP, but guess what? It turned out that wasn't my problem. Now that's the kind of problem I prefer :-).
Just saying, we don't know what our personal situation will turn out to be like. And as we all know, we can't trade problems with each other--and my guess is that probably wouldn't work out well anyway.
After the catheter came out, I used a scale to weigh the diapers to figure out how much I was leaking.

Good question. I had to use pads for 10 months. I felt jockey shorts worked best because they were tight fitting. While I longer have to use pads, I still like support and it this helps prevent an occasional leak. Also, I’m a runner and need support when I run. You will find that Amazon has lots of underwear choices. May your recovery go well.

After having a bladder cancer battle for 5 years starting in 2008 I still need the “security” of a pee pad. Just can’t get to the bathroom fast enough all the time and will “squirt” a bit. I found the jockey shorts with the stick on pads to be perfect. Actually bought a smaller size for a tight fit to keep the pad in perfect position. Wal Mart has a good price and perfect pads. In an emergency it’s amazing how much pee these pads can hold. Still have my bladder and was cancer free until recently that damn prostate cancer arrived. In my seminal vesicles as well. Gleason 7 (4+3). Having PSMA PET on 9/21/24. Best of luck to everyone. Ken

I use jockey shorts as well. The best brand of pads, IMO, are Tena. They have larger pads to very light pads which can be purchased on Amazon.

As I mentioned earlier, boxer briefs (not regular boxers) also work, because they fit snugly like jockey shorts.

What kind of pads should I get?

I found Tena slightly better than Depends, but it's a personal thing (probably a lot to do with how each of us is shaped down there). The main thing is to get large, high-absorbancy pads made especially for men.

Good info and discussion above.
My choice was Depends briefs to start out. But I was, and am, totally incontinent since RALP in 01/22.
For a year I used a local store brand "Compare to Depends" that were much cheaper and worked just as well.
And during that year I used one "Depends' brief a day but added pads (I think they were rated #8 on their absorbency capacity) and changed them when needed through the day. That was much easier and also cheaper than using only the Depends.
And not that you should plan on that. I am a rather rare case. And now I have an artificial sphincter (AMS 800) implant that works quite well. So no matter what there's a way to deal with it.
Now I use the mini (#2) brief liner for the rare leak inside my regular (Hanes) briefs.
BTW, consider just buying one pack of Depends and one of the light pads for your first week so you can see how it goes from there. All of us hope you'll be able to throw those Depends that you won't need in the trash.
Good luck with the RP and your recovery. Let's hope they get it all in one shot and you get to continence quickly.