Personally I would go with the kicker. I have trolled without one and with bags and it works but it's nice to have the extra motor and it saves hours on your main
A bag will work but after time you will get build up on your plugs. I know on my dads boat even with a bag out its tough to get down to speed. You can change the pitch of your prop to achieve the results you are looking for too. You can also also use a trolling plate as well vs a bag.
All will work it just comes down to several factors, hours on main, buildup, deploying and running bags, low enough RPMs, and of course $