I loved playing Hyrule Warriors, but haven't found anything else that worked quite as well on PC. Low point being Dragon Quest Heroes, which I was very excited to play but going from 1080p Ultra to 720p low just chenged the fps from 18 to 32 on my PC. The same seems to be the case with a lot of similar games on PC, terrible ports all around.

Is there a good Musou game on PC that is actually a good port as well?

I believe this is one of the best musou-like ports.

Keyboard prompts when using controller ruins it. :l

All hope is lost then, never found a single musou game that someone else didn't point a problem. 0.o

That's the problem, Koei Tecmo releases terrible ports.
They just can't be arsed.

Get Dynasty Warriors 4. I played the heck out of that one on PC two years ago. It wasn't released digitally but you can easily get a second-hand physical copy off ebay or something. It's the only Musou game I've played extensively but I loved every minute of it and some people claim that it's the best game in the series which doesn't surprise me at all after having also tried some of the earlier and later games in the series.

What's a "musou"?

The Dynasty Warriors series and games like it.
They use a certain basic template.

"The Warriors meta-series, known as Musou (無双 Musō?, lit. "Unrivalled") series in Japan"

The keyboard prompts aren't a deal breaker for me, I worry more about FPS, and the reviews do seem to say that it has problems in that regard.

It doesn't help that I play on a laptop running SLI, and no Koei game ever supported SLI, and I suspect a few aren't even optimized for mobile GPUs.

Wait for Berserk. Meanwhile, if you like older games, you can always try "Musou Orochi Z", or "Warriors Orochi the Collective". It is only in Japanese and it never had a translation and overseas release, even if Koei was initially preparing one... But there are many guides flying around, you can beat the game 100% without knowing a single word in Japanese! You can't find it for purchase, though. Some japanese gamerbros have shared it with the world years ago and it is still circulating (japanese netshow). You might want to try it. Nice combat, horse combat, combos, special attacks, team attacks, unlocking treasures, enchanting weapons, a really huge roster and a crossover between Dynasty Warriors and Samurai Warriors, containing heroes of legend or real historical figures! Nah, come on, you want to play as a unifier of Japan or some general of the 3 kingdoms, i know it!

One Piece Pirate Warriors 3 is widely considered a terrible port but I had zero problems with it. I think it depends on what kind of operating system/controller you're using, but I had no issues on windows 7 or 10 with a 360 controller.

Don't get me wrong, I'm actually a fan of Dynasty Warriors, but aren't they all renowned for running like shit, ports or not?

Pretty much every game in the series I've ever looked at has a load of "it runs like treacle and has awful pop up etc." and "I've never had any problems with it" comments. So its probably best to just pick up whatever interests you.
The Samurai Warriors game on 3DS is pretty good. The fact that you play four characters at once makes it a little more interesting and different than your run of the mill Warriors game.

I've still got to get Hyrule Warriors at some point, probably whenever I get back to actually playing games again.

The only one I've played recently is DW 8: Xtreme Legends, and it worked perfectly for me. Maybe I was just lucky, I don't know, but it was a pretty good port imo, despite Koei's reputation.

Shinovi Versus came out recently on PC too