Question 1 - Subscription Plan Overage Charges
No. For a Subscription/Annual/Unlimited/SaaS license, Zoom will force-limit your attendance to the subscription level. There is no "overage" capability other than upgrading your Zoom Events/Subscription license to a higher level... which, by the way, can't be done on a Monthly Subscription, due to it only being available at the 100 user level, and primarily intended as a way to "get in" at low cost and try it out. In my opinion, Zoom does not intend to allow Monthly Subscriptions at any higher level.
Question 2: PPA License Approaches
Purchased PPA licenses are "pooled" as they are purchased, with a "first in, first out" seat decrementing and expiration policy. As a brand new PPA user, buy the Zoom Sessions PPA 50 for $100, and develop your Session content. If you hope to have 1,000 seats for your event, but want to be sure you don't spend more than necessary, my recommendation is to open up registration and market the $*#& out of it, see how many registrants you have. PPA decrementing only occurs after your event lobby is open, and only when someone visits the lobby and/or the live event directly. (See Using Zoom Sessions lobby section " How to join a Zoom Sessions event lobby" for the various ways lobbies can be "joined":
https://support.zoom.com/hc/en/article?id=zm_kb&sysparm_article=KB0058217.) People who register but never join do not decrement your PPA seat count.
Thinking you might have 1,000, but seeing that you only have 250 people registered, I'd consider buying two Sessions PPA 100 licenses, for a total of 250 (you bought 50 at first, now 200 more). If, as often occurs, you get a lot of registrations the last couple of days, buy a Sessions PPA 600 license, bringing you to a total of 850. If your total attendance reaches 700, you'll have 150 licenses left, available for your next event as long as it occurs within the 1-year expiration date of the latest purchase. (More exactly... the lobby visits must occur before the license expires - it's a small detail which wouldn't affect a second event 5 months down the road.)
If you are buying your licenses on the Zoom Events Pricing page, these are the only options you have. If you go through your Zoom Account Exec or through a Zoom Partner Reseller (like me!), you can specify exactly how many seats you want at the time of purchase. If you wanted to buy 350 seats, you would pay the per-seat price of the next lower level (100 seats at $180 = $1.80 per seat) times the number of seats you want (350 x $1.80 = $630). If you wanted another 75 seats, that price would be based on the per-seat price of 50 (it's a new purchase transaction), not based on the price of the last purchase you made.
Question 3: Zoom Events vs Sessions
I just learned the answers to these the hard way recently. All of my prior clients have wanted Zoom Events, with multiple days and multiple sessions in a conference-like experience. A new client wanted only a single-session Zoom Session. If I ran her event on my existing Events PPA license, her attendees would take an Events PPA seat for each attendee - basically a 25% premium cost to have a Session attendee use an Event PPA seat allocation.
Think of your PPA purchases of Events PPA giving you a roll of green tickets, and purchases of Sessions PPA giving you a roll of blue tickets. If the event (lower case) is a single-session event created in a Zoom Events PPA Hub, attendees subtract one green ticket, regardless of the fact that the event itself is like a Session event; it's in an Events Hub, and only Events PPA tickets are used there.
Purchasing Sessions PPA tickets forces you to use a separate hub, which only uses the blue tickets. WORSE YET... One Zoom Workplace licensed user cannot be assigned both a Zoom Events PPA License and a Zoom Session PPA License! You have to assign the second PPA license to another licensed user on your account - and if you are the only person on your account, you will need to add a second licensed user to make use of it.
My advice in this case is to stick with Zoom Events PPA licenses, if you are planning to produce a mix of multi-day/multi-session events and single/recurring/Lite events. The extra expense is worth not having to deal with "which license goes where and is owned by whom."
