Glad you're still here and communicating.
Just to supplement Acey's experience, I've owned about 5 step through frames and none of them had a flex problem. I weighed 213 in 2008 but am down to 156, but the last 10 years I have carried up to 60 lb supplies plus a 40 lb basket on the back since I don't drive a car anymore. Specifically a discount store ninieties Pacific Quantum steel frame MTB step through was quite competent as a frame. Not an E-bike though. My first e-bike conversion was a seventies Huffy Savannah step-though 10 speed, quite a substantial piece of steel. That had a 20 lb basket set, and I carried 6 gallons of water (48 lb) in it. My 2017 yubabikes bodaboda has an aluminum step through frame, and doesn't flex either.
I do highly recommend disk brakes in inclement weather. I ran an Austrian 3 speed with rim brakes into the side of a car in the rain when the lady ran a stop sign after I'd stopped and restarted across. I was wearing a flourescent green t-shirt; she must have been nearly blind or stoned. Oh, the Huffy Savannah with rim brakes one time, at 2 mph I ran over a tree limb that rolled up into the front brake, jammed the wheel, and threw my on my chin. I don't think disk brakes can do that.