Whoa it does make a difference. You be surprise how critical the clearances are. You maybe only running a few thousands of an inch clearance with the gasket and have zero to negative clearances without the gasket.
If the engine calls for a paper gasket it best to use it. Now with the gaskets are commonly .015" though thinner or thicker may for clearance to be right. There are engines the use RTV, Honda bond, Yama Bond for for the sealant but the clearances are spec'd for this use. I do know if you try to assemble an engine that uses .015 paper gasket it will lock up as you tighten the screws.
When using RTV you need to use the surface prep spray so the RTV adheres properly. Before I started using the surface prep spray the valve covers I installed would start leaking in a short time leading me to redo my work. Also on the engines that uses RTV or other sealer, the sealer basically just fills in the imperfections otherwise it is just squeezed out.
Everybody perception of what is paper thin varies too.
