For me doing local alias or password storage is just not in the picture for now (sync just too vital for now). But, this could be a solution where I just keep some vital emails (password manager, alias provider) kept there just in case.
I assume best case scenario is using a separate password from password manager but considering the situation being considered could get away with using the same one with little downside.
My bank account or things that are already tied to my real identity, my main address is my full name, with all my nonpersonal accounts being routed through aliases
What I meant by local Keepass: it’s to contrast VS a cloud Bitwarden.
But you can always syncthing/else to have your own sync of it.
Not an issue for us who use KeePass.
I use an alias for literally everything except my password manager and a few websites that don’t allow aliases. The reason I use aliases for practically everything is precisely because I don’t want to be exposed to SPAM. And to me, emailing friends and family who use Gmail with my real addresses exposes me to the risk of SPAM. I even use an alias for my 2FA authentication app (Ente). My 2FA tokens are backed up in both Ente and my password manager, though.
With all that being said, I recently had a huge security crisis that completely upended my life because I depend so heavily on aliases. I will talk about it very soon.
For those, I can recommend a cheap 3$ throwaway domain name then linked to the aliasing service.
That way, you just give annoyingplace69@whyareyousoannoying.top rather than your own personal email. Small trick I found last time when saw a hostile gym being a gym. 
It also feels calm/relaxing to not be flooded with the 15th marketing email from a company in the same week with them begging for your wallet or highlight their fancy new sloppy products.
Damn, the teaser. 
I have never tried using an alias with the specific websites I was thinking of. They are too important for me to risk getting banned, so I won’t even try. I was considering asking those websites if they could allow aliases, but after my recent security crisis, I’m starting to think it’s a good thing they don’t allow them.
That being said, using aliases with a bought domain is a good idea. The only issue is that it makes it easier to identify me as the owner of all the addresses linked to that domain.
But I do think using my own domain for my own default email address is a good idea.
Is it worth buying it from a domain seller like Njalla that protects privacy when my real name will be in my address?
Indeed.
fair 
very curious to know the why here 
Yes, it’s an in-between within the 2 extremes:
It’s giving up some yet not all of your info while still having the benefit of being able to block them etc.
Oh, they do have cheap-ish domains
Sounds very decent if you can afford that.
Otherwise, you can probably save 12€ and get something with a bit more KYC from a more typical registrar and pay with fake name/address + virtual card (I was fine with that approach haha ).
I urge you not to consider exotic TLDs if you need good email deliverability. Ideally, stick to com/net/org.
I have never experienced any issue.
And this comes from a 10+ years old .io owner.
Which is a ccTLD 
but worked flawlessly for me so far.
And the trick I used with the cheapest possible TLD also worked just fine, through an alias.
YMMV I suppose.
