Set-up and synchronization questions

I am new to eM Client, using the free home version, and hitting some bumps on set-up and learning the app.  I formerly used Outlook w/ a POP3 set-up; I’m using version 7.1.30794.0 of eM Client, should be current, I only downloaded it a week or 2 ago.  Several questions:

1.  When the app ‘synchronizes,’ w/ an IMAP set-up, how does it ‘know’ which is the more current information, on the client app or on the mail server?  I’ve tested a bit and seen it change both to reflect the other, I find it a bit baffling.  I.e., I’ve seen it 
-  change info in the client to reflect changes on the mail server

  • change info on the mail server to reflect changes on the client

2.  Is there any way to change settings so that the client does NOT download spam and trash from the mail server?  I’m happy w/ the spam filters at Gmail, I can check the spam folder periodically on Gmail website, I DON’T want to download that stuff to my PC.

3.  I’ve set the app for synchronization at start-up and every 99 minutes - but it seems to sometimes synchronize more frequently than that, regardless.  (I changed setting in Tools > Settings.)  Any help?

4.  I set up one account as POP3, but the set-up did not ask me anywhere for the outgoing server port; and I then could not send e-mail from that account until I enabled SMTP.  I honestly don’t know at this point which protocol that account is using.

I think I’m probably leaning toward a POP3 set-up, because I dislike the idea of everything I do sitting on Google’s servers - such as drafts, before I decide I want to send 'em - and, at this point, I simply cannot tell w/ IMAP which source is ‘in charge,’ the client or the server, which is troubling.  And it seems that if I leave the messages on the server, w/ POP3, I can still see them w/ other devices, which helps.

Sorry for the long note and the multiple questions, but that’s where I’m at.  Thank you in advance for any help.