@Songmachine Just to add to what others have said, which is all good advice...
You specifically mention “copyright” - in the UK this is automatic and you only have to prove you wrote the song first in the case of a dispute
I think you are more concerned with understanding the royalty, songwriting and publishing splits
The best advice is to always seek proper legal advice when talking about contracts, where you need to balance the “opportunity” of getting your songs “out there” against the risk of being “ripped off” - ie not getting the share of royalties you feel you deserve
This is a really tricky balance to strike and will probably depend mainly on where you are I your songwriting career/journey
IMHO the opportunity, kudos, exposure etc. to land a cut on someone’s album probably far outweighs a % of future royalties as the chance of it becoming a “mega hit” are soooo low - and if it did then being a part of this may be more half-lives to your career than negotiating hard on the % split and risk losing out
Either way, I would HIGHLY recommend checking out joining the Guild of International Songwriters and Composers (I have no affiliation and do not get a commission):
https://songwriters-guild.com/I haven’t been a member for ages but they offer a copyright service AND legal/contract advice as part of the membership. They also offer a song critique service and other benefits
This is probably the cheapest route to specific music industry contract advice and guidance
Good luck and please keep us posted on how you get on