I think that's an oxymoron 🤔
Surely you do want bells and whistles on your sound equipped loco's? 🙂
But seriously, sound equipped loco's from Bachmann, Dapol, Accurascale, et al, frequently use function keys up to F28, so a simpler 'cheap' controller might not support that.
As @Steven B said, it's a very good idea to visit a specialist DCC retailer and try out different systems, they can also advise on which systems would meet your needs.
Regards,
John P