modal verbs - What is the difference between would and might?

Me: Hey damn why isnt he picking the phone up
Friend: He might be having the lunch / He would be having the lunch

Me: Looks like it's going to rain today I should take my umbrella with me
Friend: That might be better / That would be better

Me: Of our friends who do you think might have attended Chainsmokers concert last week?
Or: Who you think would have attended Chainsmokers concert last week

The words would and might being a non native speaker sounds alike to me...

To me, I guess they both can be used for guessing. No?