I assume you mean rims and hubs. Yes bearings contribute to resistance but unless your bearings are in terrible shape, then no, drag caused by bearings is not going to make any difference to the drag caused by the rubber on the road. Your rims, hubs and spokes create drag, but that’s aerodynamic wind resistance, not rolling resistance. In fact, just having the wrong tire pressure could create more resistance than your bearings. Perceived smoothness can come from a variety of factors, but smoothness perceived by the rider doesn’t necessarily equate directly to decreased rolling resistance. If 50 or 51 is the max, then certainly max it out, because there is practical efficiency to be had, especially from a larger rear sprocket. you need to figure out though, wether you’re more interested in acceleration (sprinting) or more interested in a higher sustained max speed. Because these require very different ratios, and you need to think carefully about the type of riding you’re going to be doing, before spending money. This, in my opinion just stresses my point that wheels (and behind that, tires) are the most important 1st upgrade to spend your money on.