I know the Mepis forum members are a very knowledgeable and helpful bunch which has rubbed off on me. I was a clueless Linux user till I tried Mepis back when it was Ubuntu based instead of Debian based like it is now. You'll have to learn to use KDE which is the default Desktop Manager.
I run the lighter version AntiX.
All I can say is there are some pretty computer savvy people running 64bit Mepis Linux.
Best and Latest Isos I know of available from a Mepis user/guide who is well respected, just my opinion. Might be worth trying out maybe.
Good Luck and Happy Trails, Rok