how old are you?
first off, is this self prescribed TRT or legit from a doctor? if its from a doctor and you are a new HRT patient, as far as i know they schedule monthly bloods to dial your levels in. cause if you're new and your doctor is still monitoring you monthly or even once every two months, you can not fuck with your dose. he will know somethings up from the bloodwork and you'll lose his trust.
second, 7-800 ng/dl for 200mg test a week sounds a bit low especially if you're using HCG. you should be at or above 1000 easily. you probably pin once a week and got those bloods done a day before your next injection, am i right? try pinning 100mg Mondays and Thursdays.
as far as bodyfat, 15-20% is a huge difference bro its day and night. either way, if i was 15-20% my only goal would be to cut cut cut. with AAS, gaining lean mass is way easier than losing fat so i always think its more logical to get as lean as you can before you attempt to build muscle. IMO, what good is a chubby 17% bodyfat dude with lots of muscle?
i'm gonna assume you're 15%. 5'10 200lbs @ 15% is a pretty big dude. if you work hard and cut till the end of April you could probably get down to 10%. then on the first of may you hop on 500mgs of test and with the right lifestyle you can easily gain 20-25lbs of lean mass in 12 weeks. lets say that all equates to 5'10 200lbs @ 10% bodyfat. those are some fuckin great stats right there.