A straight 30 or 40 is perfect for the drippers (that indeed go to the main bearings). I always use what is available and never notice much difference in thickness. On a two/three speeder with the oil tank behind the rad you have to adjust the drippers every now and then as the oil heats up because of the hot air coming from the rad and the oil get thinner.
I do premix a bit of two stroke oil in the petrol but that is mainly for my own peace of mind. The bike sort of seems to run better with a bit of premix…
PS just be glad you do not have the pilgrim. Just another thing you don’t have to worry about!