I'll preface this by saying I used to work in the industry.

The restriction evading isn't really related to the number of servers. VPN companies for streaming block evasions buy IP addresses that aren't data centre specific. Those ranges are well known and easily blocked. So for example when you browse you'll generally use a "standard" IP but while connected to the same endpoint if you fire up a netflix session it'll route that traffic out the "streaming" IP. This is also partly to try to prevent steaming companies from getting easy access to a list of those IPs

It's quite expensive to get IPs that aren't blocked by steaming services so that is a cheaper cost per user for larger companies. Where I was that cost was way more than the cost of any individual server per month (and some of those servers were hefty). That is one way that Mullvad would have an edge but it's minor.

For what it's worth I did have a call with the iVPN lads (twice I think) and found them lovely. Never interacted with Mullvad but I will never give them money after reading this. Weirdly I'm in the market for a new subscription and they would have been my go to. Their fiver a month thing is really very smart.

Edit: for geo blocks on standard browsing it would generally present to us as a support ticket. We'd raise it with engineering and they'd assign a new outgoing IP with whoever our provider was. We used M247 a lot and they were very responsive when that happened. Usually a few hours and it was sorted.