Handling multiple map frames with different layers in one print layout?

Use groups of layers to simplify your editing and then don't lock the frame by right-clicking on it but instead use the 'Lock layers for map item' check box in the Map tab.

I group my layers according to the map frame I want them in. Then, I can quickly turn on and off a set of layers as I set up the map frame the first time and then click the 'Lock layers for map item' box. When I want to change one map frame and not the other one, I can just work within one group. You may want to duplicate a layer in each group if required or if you want different symbology for the same layer in different frames.

When you click 'Refresh' from the View menu only the selected currently map-frame is updated unless you have any additional map frames which are both unlocked (no padlock icon by right-clicking the frame itself) and do not have the 'lock layers' check box selected.

Working with layer groups and item locking in this way is pretty analogous to the ArcMap setup except if you want to change the projection of on map frame and not the other.

You should be able to handle most of what you are doing by using the scale dependencies for a layer.

so, map 1 is at 1:5,000 and map 2 is at 1:50,000 you can then change the sybology in whatever order or have them all visible and one map would not influence the other. Essentially using the grouping technique but based on scale rather than map frame.