sleep mode question

This comes under the heading of whatever floats your boat. Either way, no worries.

 

Doesn't really matter. Closing might protect the Mac better in case of some stupid accident.

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SLEEP means, that all active content in the RAM just stays there, in the RAM, and only the RAM is powered during SLEEP. Thus no CPU is used. No need to quite applications for letting a Mac sleep.

Btw, this may be helpful:

Helpful Information for Any Mac User by GGJstudios​

 

You don't need to leave the lid open for cooling purposes, even while running, as Mac notebooks are designed to run in clamshell mode with the lid closed. There is no venting through the keyboard. All venting is at the rear, near the hinge.

 

If you want to make the MacBook sleep the same way as closing the lid only instantly, you can try one of two things that will lead to the same conclusion:

Ctrl+Shift+Eject

OR

Apple Menu > Sleep