Generally, what % of the time can there be an immediate load dental implant placed in the upper right molar area? I know it depends bone loss/quality.

Not often. Immediate load in the molar area on a single tooth is usually contraindicated. If you are doing a procedure such as all-on-4 in which implants are connected by a bridge on a temporary basis, immediate load can be done. On immediate load on single teeth it is necessary to not chew on that side for approx. 3 months. The name of the game is success and loading a single tooth in function is not wise.
Undetermined. You already know that it is dependent on bone quality, location, & occlusion, and that is determined on a case by case basis. Immediate loading can work, but in very limited situations. Weight the risks vs the benefits before taking this route.
No rules. There are no specific rules or guidelines concerning immediate loading. Therefore i cannot give you a percentage. It is based upon many factors and left up to the judgment of the restorative dentist. I personally do not favor immediate loading, especially posteriorly when it is not necessary. I fully understand that other dentists may not agree with me. Immediate loading can be very successful.
Guarantee? If i were to have a dental implant in the molar area, i would like to believe it had a 100% chance of success. Immediately placed dental implants have a lower success rate, than those placed in healed bone. Implants immediately loaded have a lower success rate also. Do you want to take chances, play the odds?
Depends. As you said bone quality. In the back why chance immediate load. Just wait. Some times you can place the abutment and a temporary crown that does not touch the opposing tooth until the you are ready to load it and be in occlusion.
Spends. Depends upon the height and width of the availed bone. Amos immediate load works best in sites where the bone is already healed. In a molar site if an implant of at least 6mm diameter and a length of 11-13 mm can be placed then you are good for immediate load.
Unknown. Often this area of the mouth has poor bone quality and the maxillary sinuses can be low. This means there is inadequate bone quantity and density for immediate load dental implant. Consult your dentist and often a ct scan of the jaw will be taken. Good luck.
No special % We do not like to immediately load any single molars. We frequently immediately provisionalize them, but we keep them out of occlusion (the bite) . If we replace an arch and can splint 4 or more together, then we can immediately load them, although we recommend soft diet for about 3 months. If 2 implants are placed in the single molar area, you get a splinted effect of sorts, but still no load.
3 to 6 months? You don't want to load an implant, especially with a bone graft, until the bone has matured to where it can withstand function. I don't like to load an implant for at least 3 to 6 months but also check the bone with some form of radiography to be sure it appears healed/ready to receive the implant. Don't rush mother nature; it takes time to heal.
Stability is key... The upper molar area can be more challenging for immediately loading a restoration due to the tendency for softer bone. However, if implant stability of 35 ncm can be achieved, and the implant is at least 5mm wide and 10 mm length, with a stable occlusion and no excursive interferences, you can successfully load the implant immediately. This is probably 30% of the time. Keep smiling !
Not recommended. Immediate loading can be advantageous in some situations. Specially in the aesthetic areas of the mouth or full arch provisionslization(all on four technique). Iimmediate loading of a single molar however, does not provide any more benefit to the overall treatment plan.
No advantage. I dont do the procedure you are asking about. You want to maximize your chance of success. Immediate load decreases the chance of success a little. There is no advantage.