L visa and f type- so you need an f type if you already have a L type permitting entry for 90 days

if one already carries an L type, and is now needing to obtain a an F type will the L type be invalid once the new F type is purchased? Or can both be carried at the same time?

Is there a need to purchase a business F type if one already has a tourist L type as they both permit 90 days stay per entry?

From Uk. Thank you.