I too experienced lagging when tagging in my 130k files music library. I usually did tagging with split views (2 views) consisting of pane views each with 11 panes, often construed from expressions. Saving a change to just one song could take several seconds during which time MC was unresponsive, so I experimented a bit. (Slow writing to file tags, or antivirus protection, was not the issue, since changing a field was equally slow if write changes to file tags was turned off.)
Tagging with just a single view with the 11 panes view was just, or at least almost, as slow as before. Tagging with a single categories view, even with the file list shown, was, however, almost instantaneous (but not an optimal environment to tag in). I also discovered that having a spilt two views setup where the panes view was hidden and only the categories view visible meant that tagging was as slow as with only the panes view. Having multiple tabs did not affect tagging performance.
Since I want to tag with a panes view I experimented further and found that a panes view seems to be faster for tagging the fewer items there are in the panes (at least with no bi-directional filtering). I therefore removed the two panes with the most items (92K and 35K items respectively). I also converted the very first pane to a search list with only a couple of items that will when selected show only a subset of the total number of files in the subsequent panes and in the file list. I furthermore moved the remaining pane with the most items (27k) to the right so that it is more likely to be fewer items in that pane when tagging (because something is selected in the panes to the left of that pane). Now tagging is fast once I make some selections in the panes to the left.
To summarize: Try to avoid having panes with very many items. Whenever feasible sort the panes so that panes with fewer items are to the left and make as often as you can selections in the leftmost panes. (I am of course talking about horizontal panes view.)
At least these guidelines helped me and tagging is now fast (but not as optimal as I would like).
I do not search very often and had not experienced any performance issues with searches.