Windows 11 with Android installing need 16GB RAM.

For Dell prebuilts , the proprietary stuffs are:
1. Motherboard -> non standard form factor.
2. Power supppy -> non standard , especially the connectors and form factor. Not ATX , SFX or TFX
3. CPU cooler -> the holes are not the same as AM4 or Intel LGA spacing.
4. Casing - the power on button , reset connectors to the motherboard are proprietary.

The above stuff you have to buy replacements parts from Dell. Usually is refurbished only. Or used online from 3rd party seller.

Dell support is very good. I agree. Because even if u live in the jungles  of Borneo , they will do onsite support warranty service for u. But hopefully u get 3 yrs warranty , usually stuffs can fail around 1 1/2 years if u are unlucky.

Gtx 1650 is not going to last u for 5 years. All the available local 1650 are not even the super variant.
12400f +b660 ddr4 will serve u well. Just wait for Rx 6500xt or rtx 3050 and see how it goes.

Use NVMe, not SSD

select ...

1) 1x16GB RAM straight
2) 512GB M2 NVMe
3) GTX 1660

after that good to go