So I've finished the game and I'll tell you this. Lies of P is it's own thing. Don't believe anybody who sits on this forum and tells you it's just like BloodBorne. It's not even close. That's not a good or a bad thing. The games are simply...vastly different.
That being said, Lies of P is also a great game. The story is good and well told, so if you prefer this kind of story telling vs. what you get in more obscure Soulsgames then I think you're in for a treat. The weapon system is very unique, though, in my experience, the boss weapons is where it's at...and unfortunately those can't be mixed and matched like non-boss weapons can.
This kinda leans into combat, which is kind of a mix between Souls and Sekiro. Yes your attacks have to be timed and intentional, however the parry system is much more unforgiving than Sekiro IMO. Literally it's just frame of time you can successfully parry is longer in Sekiro. You have to be more precise in Lies of P. What's great about some of the weapons is that they come with arts that are like an auto parry which can make things a bit easier. I found that a Dex build is simply better than the strength builds I've tried, mainly because there is no poise armor for doing slow and heavy strikes, which mean you can be interrupted alot. This just means you should use Dex weapons and save on stamina.
The upgrade system is not just useful, but I'd say pretty much mandatory, you should not ignore it. It will make your chances of survivability against certain enemies and bosses much higher. For example, there is a cooldown on dodge rolling in the beginning of the game. You can upgrade so that you can dodge roll back to back with no cooldown. There's also an upgrade to allow you to roll after getting knocked down. These things are taken for granted in Sekiro and Dark Souls 3, but you have to earn it in Lies of P.
Level design is not as connected as Dark Souls 1, but there is some sense of connection there as some of the levels are pretty big. Definitely there's some off the beaten path kinda level design going on but they typically wrap around to the main path or are dead ends with some reward in them.
I don't wanna spoil too much, but it's fairly lengthy, you'll definitely get your money's worth out of it if you're a Souls fan.