Hi o/ welcome aboard 
One of the trends we’ve seen in the last 3-4 years has been a surge in new players who’ve heard about Empire via YouTube videos. They’re in the main a lot younger than us old fogies So yeah I wouldn’t worry, there’s loads of people around your age playing or about to start playing when the world lets us.
Nation size wise, it’s difficult to be precise without numbers from PD but the nations are very roughly (bigger to smaller):
Wintermark
Navarr
Dawn
Highguard, The Marches, The League
Varushka
Brass Coast
Urizen
Imperial Orcs
And the last time we have numbers from PD (2019) Varushka was 159 and Highguard was 232.
BUT there’s been a lot of new players who’ve been wanting to come along since the last game ran and they’ve been able to. So I’m expecting a large influx of new players in all nations next game, whenever that is .
So I wouldn’t worry about there not being enough people to find fun with in either nation.
The new player team run intro sessions on the Friday of a game before time in, if you get along to that you should get introduced to your nations Egregore. In game they’re avatars of the spirit of the nation, but Out Of Character one of their jobs is to make sure new players get involved and have a good time. These sessions are also really good for meeting new players who are starting in your nation. Teaming up with people in the same position as you is usually a good move and actually something I’d recommend over joining an existing group.
You can also find groups and put yourself out there by joining the nations FB groups as mentioned above. Getting an introduction online and then trying out whether you get on with people at the game is pretty standard. But also just turning up and wandering round introducing yourself to people on the field can also work quite well. I know my group in Highguard don’t recruit people we don’t know, but we’ve picked up a few people in game after they’ve hung out with us for a game or two.
And yeah like @Triska says what do you like about Varushka and Highguard (she plays in Varushka and I play in Highguard 
)? Ask us anything you like.
(Also that’s given me an ideas for some forum threads…)