Yes.
1. The estimated time (based on using my firmware) is shown on the laser controller after you generate the G-code. You can adjust the estimate factor if using different firmware or parameters.
e.g.
GCode Lines: 13
Estimated Time: 4 seconds
Total Distance: 60mm (c50/r10)
2. Use the trace or engrave frame option, set the manual laser power value to 5 if you want to see it but not burn or higher if you want to burn into a wasteboard and use that for alignment.
3. T2Laser supports cool down for vector (cutting or line engraving) but it should not be required for engraving as the laser is never at full power for long periods of time. The laser uses PWM (pulse width modulation) so the laser is actually switching on and off quickly so doesn't heat up as much as when continuously on like for cutting. I have ran my EleksMaker laser module over 6 hours for many jobs and a few well over 12 hours. The longest ever was nearly 18 hours and the laser module was no hotter than it is after 15 minutes - a good fan and correctly sized heatsink are essential.