Does Chrome run in separate processes/sandboxes?
Yes. Chrome runs in separate processes on Android.

This is what I get from ps -aux | grep chrome in a root Termux session:

u0_a128  14180  5.5  2.2 1530600 175948 ?      Sl   13:04   3:55 com.android.chrome
u0_a128  14418  2.2  1.0 1412520 84168 ?       Sl   13:06   1:31 com.android.chrome:privileged_process0
u0_i9    21115  3.0  1.1 1428008 91124 ?       Sl   14:07   0:13 com.android.chrome:sandboxed_process6
u0_i14   22492 16.2  1.2 1548252 100956 ?      Sl   14:14   0:13 com.android.chrome:sandboxed_process11
root     22686  0.0  0.0   8748  1524 pts/2    S+   14:15   0:00 grep --color=auto chrome