Cash as payment option

Yes, and even in China, the refusal to accept cash is an inappropriate behavior that can be reproached at least and can lead to administrative penalties.
However, given that online payment methods have been widely used by the whole society for many years, in many cases, it is not that people do not want to accept cash but they really don't have notes in wallet to make change, or they just don't want to waste time (but at the manual toll window in public service places such as train stations and subway stations， you can pay with cash with confidence).
That's why I recommend that you to use Alipay and WeChat Pay as much as possible in this country (you can also use the boarding QRcode on the software when taking the subway and bus).Then,you can not only save the trouble of exchanging cash, but can also enjoy the fast and convenient experience brought by mobile payment.
I hope you can have an unforgettable trip in China!

Do hotels and convenience store in china accept top up alipay for foreigners? Can we exchange cash with alipay/wechatpay top up?

Sorry, hotels and stores cannot top up alipay for you and some store owners may agree to exchange with top up but mostly you may be refused.