IMO, this is similar to rogue legacy for those wondering on gameplay style, you slowly unlock better items that let you get further each time
Sort of, they share having persistent upgrades but Dead Cells has progressive levels with different branches to explore, while Rogue Legacy has one big level. I'd say that Dead Cells is an all-around much better game. The controls are more fluid and feel great to play with, the combat is much more fleshed out, the presentation is better and there's more variety to the gameplay. That last one is done by having different weapons to play with, more enemy variety to fight against and importantly more upgrade paths both across runs and over the course of them, which includes being able to upgrade your character through getting better gear, skills and level ups and not being limited to using what you start that run with.
To compare, in Rogue Legacy you pick your descendant, which gives you the regular sword swing, any special trait they have and their special ability. In Dead Cells, you start the run with two pieces of primary gear randomly picked from all the gear that you've unlocked up until that point, which includes axes, boots, shields, spears, daggers, bows, magic, whips, and more, and you'll quickly get two pieces of secondary gear that represent your skills, such as different traps, flashbangs, flash-step, turrets, vampirism or a grappling hook. All these pieces of gear, barring the stuff you start with, also get secondary traits that alter how they work, such as doing bleed damage, freezing surrounding enemies after a kill or having you do double damage while also receiving double damage, which is how you tweak your build in addition to the different types of level that you can get. Dead Cells does get harder than Rogue Legacy, but is more fun to play which makes restarting less of an issue. It's a great game for if you just want to pick up and play something.
How is the game treated by dev here overall? Is GOG getting all updates and fairly on time? Is it missing any content here? Are tere some features locked behind Steam? Is planned release at least roughly the same or will we have to wait weeks or perhaps months?
Anything else I should know?
I want to buy the game but I don't want to get inferior product and suppoert comapred to Steam customers.
So far the updates have been very timely, same day as on Steam or only a few days afterwards. GOG has all the same content and features, which includes the daily runs. You also don't need Galaxy to do the latter, all you need is to be on-line, unless you want to upload your score to the leaderboards. Nothing so far suggest that any of this will be different for the final release.
If you happened to play Dead Cells, maybe you could let me know, is the story as slash your wrists emo, as the one from Rogue legacy? Because that's what I hated the most from Rogue Legacy.
Story hasn't been introduced yet, but what is there is more towards the weird in tone than edginess - you're kind of a sapient pile of goo possessing a headless corpse, so it's doubtful that there'll be any familial drama. I don't think that it'll end up a game that you will be playing for the storyline however. The gameplay is what you'll want to get it for.