Which UTMSimple Plan is best for me?

We have three plans, Basic, Plus and Unlimited. The primary difference between them about the traffic your website gets monthly.

If you have a traffic up to 5k monthly, then you should pick Basic plan If you have a traffic up to 25k monthly, then you should pick Plus plan If you have a traffic more than 25k monthly, then you should pick Unlimited plan

No idea, what your monthly traffic is, go to your Google Analytics. Select Audience > Overview. Make sure you select a one full month (e.g. previous month). And the PageViews is the number you need (see below).