"Normal" scale will make the scaler abide by your vscale_mode setting in mister.ini. If its 0 it will fill the screen, 1 will be vertical integer scaling, 2 will do half-integer steps, etc. Many (but not all) cores that have a 5x cut/216p option require vscale_mode=0 for it to work.
V-integer will mostly ovveride your vscale_mode setting and force a whole vertical integer scale, with the horizontal following the core's aspect ratio.
HV-Integer introduces whole horizontal integer scaling. By default it will tend to go to the closest whether that's wider or narrower. + will force it to go wider than default (round up) while - will make it go narrower (round down.)
Things get complicated if your output is actually wider than your display resolution (i.e. some handheld cores for 4:3 output. Also vscale_mode 5 and 6 change the output resolution by logic I don't fully understand.
Most of these settings have no effect on the analog output (unless you use vga_scaler, in which case all of them do.) The only one that tends to have an effect is the settings some cores have for visible area (i.e. border or 5x cut.) Even in that case its not going to add a framebuffer, that would only be for a handful of handheld cores that have explicit buffering options.
