Interesting Eagle! ^
So I ran some numbers on the OPs question.
The OP states 'beginner' so I assume no engineering yet. I built a basic A-rated Eagle with D sensors and life support.
With all optionals empty aside from a shield generator, the A-rated Eagle gets speeds of...
262/382 with 3A thrusters
335/489 with 3A Enhanced Performance thrusters
If I then load every empty optional with a HRP the numbers become
256/373 with 3A thrusters (minor change)
306/446 with #A EP (significant change)
This ignores agility considerations and focuses on just speed. With the 120 optimal mass of the 3A's. the additional armor makes little difference. But if you opt for the EP's, it makes quite a big difference due to the lower OM, though it's still faster than a lightweight 3A build. So in a stock A-rated Eagle armor isn't going to be too much of a drawback. And it takes the integrity from 74 to over 400.
The surprise was how slow a stock Eagle is. I remembered them as a little faster. That's way too slow for such a squishy ship!