At the same BMI (Body mass index) like same height and weight. After HRT you will look fatter than before HRT. Before HRT we will likely to have more muscle than fat and after HRT you keep losing you muscle and gain more fat.
The best way to find out the best weight for you is to keep monitor yourself. I find that my best weight keep changing, when I was guy, I look average at 160lbs, then I lose to 130 lbs before I start HRT and I look like a pencil at that time, like super skinny my face was like bone face. Then I start HRT, after a year on HRT, at the same 130 lbs weight, I do not look super skinny anymore and my face start to fill up.
And also I find out one thing, when I am skinny (for me skinny is like model skinny) I kidda look good on my cloth. But when I am a bit chubby I think it look better when naked ^__^