Funny enough, I haven't tried using the speech bubbles on the events that will be event template-ed! The mere presence of seperate/other npc events on the map with the speechbubbles will cause a crash.
I did some experimenting on a fresh project and I figured out that weirdly, it seems to be an odd case where the presence of the EventTemplate Plugin causes something within the SpeechBubble plugin to fail to read itself.
Here's video1 of it working without the speechbubble:
https://tempclip.com/XQZCRoUtrtrG2s6/watch
And here's video2 of the speechbubble enabled causing a crash:
https://tempclip.com/OwMCHh6UghRZop4/watch
Although! Recently I figured out that commenting out this part of the SpeechBubble plugin's code:
return !!event && NOTETAG_BUBBLE in event.meta;
prevents it from crashing but I end up losing the ability to use the two bottom example event speech bubble commands...
Here's the simple test project on a temp upload thing: