Can't comment on
Realme, but from UX pov, stay away from
Redmi devices at those prices. They do offer relatively good hardware for the price but the MIUi is not that optimised for low end devices. Given the budget, only 4/64 would be available and their custom rom itself takes up 3-3.5gb ram so it would be slow overtime.
I won't be wrong to say Miui software works the best on
Xiaomi devices, followed by average on Redmi devices and worst on
Poco devices. Personal experience, using Poco X3.
Oppo,
Vivo I don't think they get any updates at those priced phones.
Given your use case, I think any phone from the above brands would work. The only issue comes is Ram/Rom config. If you don't intend to use phone for more than a year then get any one. Lower segment phones are designed to work good for 1-1.5 years.
You can look for Redmi 10 Prime. Costs 14,500 for 6/128.
I think
@ijsa has Realme 8i, perhaps he can offer some insights on Realme and offer some long term review.