Ya rgba has some limits atm. ribbon brush would be needed.
you can still create amazing stuff with rgba:
d4cd0df3360b8854d2a2f9adc957701c0deb2f98.jpeg (1920×1920) (krita-artists.org)
but it does still suffer a bit from the gap
you have to make brush tips that don’t have that gap: like that one:
you maybe want to try Heavypaint and incorportate it into your workflow: oil brush feature:
HEAVYPAINT Oil brush | Feature Preview - YouTube