You want to leave bass and drum tracks to the outer tape tracks if possible as you'll get less bleed to adjacent tracks. Also, if you think about it, once you combine and bounce tracks, obviously you'll record over the original tracks and they'll be gone. So from a practical point of view I'd bounce to tracks that are easier to re-do if you decide you want to rerecord them. Also assuming your drums take up two tracks for stereo separation, you wouldn't want to place a lead vocal over one of those if you want the track panned centre, since the drum tracks will be panned L/R--alternatively you can centre the vocal over both while panning but then you're committed of course. If you want to effect a track, you'll need to do it while bouncing, otherwise you'll effect everything. A few thoughts.