If you work on and/or maintain good flexibility and muscle balance for both upper and lower body combined with a proper fit you will not have to worry about form per se while pedaling in the saddle. The preceding will by default have you maintaining proper form. You will automatically pretty much always naturally be in the proper form. The proper form varies from individual to individual so you shouldn't be overly strict on trying to maintain a one type form for all is the right one.

Riding out of the saddle on a climb does produce different and greater forces on your knees. However, if you use proper form, (you will have to develop that), and you have healthy knees you will be fine there too. At a certain point in terms of weight the heavier, a rider is the more difficult it is to climb out of the saddle. You won't find too many 200 pound or 200 plus riders coming out of the saddle very much especially on longer climbs. (And the older they are that amount will get less after a certain age.)