In ROS, everything you type is applied immediately and permanently (unless you use safe mode).
During initial configuration you can decide to use QuickSet and one of its modes. I guess that bridge mode is the one making device a basic switch. When selecting router, it’ll probably use first port as WAN port and possibly add firewall rules. But none of QuickSet modes cover multiple VLANs (and routing between them), here you’re on your own.
Since you’re still showing interest in QuickSet: after setting anything outside QuickSet windows (either the nornal GUI or CLI), never ever go back into QuickSet part of GUI. It’ll mess your config in random ways making your mother cry.
As to the management port (ether1): it’s not connected to switch chip, rather it connects directly to CPU. So any traffic passing it will bother (not so fast) CPU. So it really is meant only for out-of-band management and thus no VLANs are necessary. But if you do so, then yes, it’s normal to loose access … unless you prepare a few things beforehand. And that’s true for in-band managenent as well (if you go for it … many devices don’t have dedicated management port and in-band management is commonly used)
I ferl that you want to learn more about how to do VLANs on Mikrotik (including routing), so I suggest you to study this great tutorial. When dealing with bridge, it’s important to understand bridge’s multiple personalities.