I'll take a shot however it has been so long I may be wrong.
1 - Do func_details and hints have any disadvantages to them?
2 - I've overscaled my map, can I just resize it with the Transform tool or do I have to start over?
1. Yes they do not block VIS since they are not drawn. Since they do not block though you can see the whole area behind them which if you have a lot of brushes or detail EVERYTHING will be draw and slow down your pc. It is good to use them for detail, not for world brushes (solid groud, solid walls etc)
2. You could however it will result in most all if not all your brushes to be off grid meaning if you even wanted to make an adjustment later it'll be hell.