A few findings from my side if you want some feedback, I generally work mosh'd into some beefy servers with a long running tmux I resume -- so I'm probably the use case this is aimed at (client: xps13, archlinux).
1) If I create a vertical split view (tmux_key+v) while I already have some output in the left side of the split, and have nothing but my prompt in the right side; then resizing the split is instant/snappy.. However, if I then do a find / in the 'new' (right) split, ctrl+c it after a moment and then resize it lags/judders hugely -- I'm not sure what's going on there but let me know if you'd like me to try and explain that more if you can't reproduce from that.. This doesn't happen in termite..
2) I had to set offsets and use a giant font to make it look reasonable on my (highdpi) lappy:
font:
normal:
family: SourceCodePro # should be "Menlo" or something on macOS.
style: Regular
bold:
family: SourceCodePro # should be "Menlo" or something on macOS.
italic:
family: SourceCodePro # should be "Menlo" or something on macOS.
size: 26.0
offset:
x: 4.0
y: -30.0
+100 :}