Personally, and I know not everyone shares this view but it is my opinion that if someone has a healthy level of systemic estrogen, then unless there is a specific issue relating to pelvic blood flow, scar tissue, radiation or neuropathy etc, they should not have GSM.
GSM is caused by a lack of estrogen, and doesn't occur in women with healthy, unimpaired ovarian function.
Given the biological implausibility that every other estrogen sensitive tissue is thriving at a particular level of replacement whilst your vagina is uniquely atrophying, I personally would not use vaginal estrogen as it can mask this helpful indicator of general estrogenisation.
I would rather have my vagina be the canary in the coalmine alerting me to systemic undertreatment given the impracticality of getting a DEXA and a coronary artery calcium score every few months.