Playing vs AI is OK, but it will get you into bad habits when it comes to playing vs people.
Dip your toe in the water and play vs players and see how you get on with UEF and any other faction you fancy trying.
Fatboy has the longest range of all mobile land experimentals. That can count for a lot. Kiting is the way to go when they would be killed if they stood still or advanced.
They are mobile factories, which is a nice to have feature. 4 or 5 of them with an army adds up to critical mass in most situations.
Titans are great for wiping out T1 spam and pretty good vs T2. Percies are great vs T3 and T4.
In 1v1 battles about 8 Percies with a mixed T1 and T2 army are normally sufficient to push for the victory and win the game. Critical mass.
And then there's the Tac Nuke on the commander. As well as the massively under-used bubble SACU's. Check out the WilloWisppsi youtube channel for some inspiration on having fun with UEF.
The T3 PD's in sufficient numbers with shielding are what helps with defence for UEF, especially in bottle-neck land areas. Especially vs AI.
For navy UEF have the T2 shield boats and the T3 Battle Cruisers. Both are nice units.
The T2 fighter bombers can be devastating in sufficient numbers with their napalm attack.
The T3 Broadswords are great vs ground units. Especially vs AI great for killing land experimentals as they approach your base.
And if you get to an income of 900 or more, the Mavor becomes buildable. Keep it alive and it's a highly potent game ender. They work very well in conjunction with a Defence Satellite that's spotting targets. Or just use a combination of traditional T3 static arty and satellites.
One of the strengths of this game is the rock scissors paper nature. If UEF were only good for turtling and were no good on offence it would make them a one trick pony. They're more than that.
Map control counts for a lot in this game vs human players. If you go into such a battle with the strategy of turtling, like you might vs AI, you're setting yourself up for a loss.