For the most noticeable upgrade, strive to obtain a card that is at least two FPS tiers higher from your current, using Toms Hardware's GPU Hierarchy chart:
An RTX 3060 would be the next step higher, being on par with the RX 6600 XT
MB is an amount.
MHz is the clock.
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GPU Clock is the speed of the Graphics Processor in MHz (what you're looking for).
The VRAM in my OSD (shown) is the amount of video memory used.