New bike suggestion

[valkm1]

Hi, I am purchasing cycle for first time. I am 28 year old Male with minor back pain (mostly due to sitting).

Please help me make my purchase at BikesDirect

Past Cycle:
Age 8-14
image.png
I was child/teenager, ended up riding my sister's bike. Thin tires, higher bar.

Requirements:
1. I have been used to riding bicycle with higher handle bar and low seat.
2. I am going to use for both indoor with bike trainer for peloton/zwift and outdoor (v. light trail and mostly road). Indoor more often.
3. Bike that will strengthen glutes and to avoid low back pain.
4. Budget less than 300-400$ (new/used)
5. Not looking for cruiser, bike from my childhood

Human Specs:
Weight - 168 lbs
Height - 5 feet 8.5 Inches
Cycle Inseam - 31.5 Inches

Location: San Jose, California

Question:
Being health conscious suggest for good anatomy for comfortable ride (with view on long term benefits). If you would say go for flat bar and low handle. I will listen.
1. Suggest good bikes for both road bikes, hybrid or others (mostly might prefer road) with requirement. I watched many Global cycling network YouTube videos.
2. Compatible bike trainer (budget less than 900$, mostly Tacx Neo 2)
3. Other gears useful for biking. Size M with my human size?

I really appreciate your help a lot. Please let me know for any additional questions.