Someone says that it can increases the fps because vanilla launcher uses less more ram rather than ftb one.
Can I just copy ftb mods folder and paste it into .minecraft folder?
And install the forge manually?
That someone had no idea what they were talking about. But yes, if you want you can do exactly that.
1.) Get a vanilla client of the appropriate version
2.) Start up client
3.) Close client
4.) Install Forge manually via the instructions provided - choose the same version that was used in the FTB pack
5.) Start up client
6.) Close client
7.) Copy over the /mods folder
8.) Copy over the /coremods folder
9.) Copy over the /config folder
10.) Start up client
At that point you should be done. Theoretically.