Of my limited knowledge about HRT, it's the estrogen that causes the risk if blood clots. Cis women taking birth control have the same issue. Smoking increases that risk tremendously. From what I've read it doubles the risk. When I started HRT my blood pressure was high as I'm a smoker also.
I don't know what options are available to you, but I chose to get estrogen pellet implants as it carries the lowest risk of blood clots. Injectable estrogen is the next safest, with oral estrogen being the highest risk. From my understanding, it's the spikes that cause the issue. The more level and constant the estrogen, the safer.
As for taking an anti-androgen like spironalactone alone, I'm not sure just how much feminizing you'll likely experience. Others may know better. I started Spiro at the same time as estrogen pellets. I do know that long term lack of both testosterone and estrogen can lead to other health issues like osteoporosis.
Sent from my SM-G930V using Tapatalk