Yes and no.
Pending means the sub hasn’t gone through to the home instance of the community. If you’re the first subscriber, this means the there will be no inbound federation bringing the content from that community to your instance.
If someone else on your instance has already successfully subbed, the federating is already occurring, and your instance will be receiving the activity as it comes in.
Your instance will then show it to you, both in your subscriptions and in general, even though the sub is pending.
If your sub stays pending, you may have to unsub and resub to get it to work. If no-one else on your instance has subbed either, then the activity will continue to not show up for as long as it is pending.
Start with the cheapest plan.
If you ever find yourself wishing steam installed a game faster, then upgrade to the next best one. See if that feels like enough.
I pay a bit more for 600mbps, but that’s because I have a home server which runs services for friends and family. It might be streaming media, be syncing nextcloud data, and uploading a snapshot to off-site backup, all at the same time, and it needs to do that without hiccups for anyone accessing it. Even then it’s more than strictly necessary. 350mbps would be VERY fast, and enough.
Along with that comes the ability to install small games basically instantly on my gaming desktop, and big ones in the time it takes me to grab a snack, but even the cheapest speed available would otherwise be more than enough for single-person use.
My siblings and mother live on 10mbps home wifi, and they never even complain.