Mixed development issues of uni-app and native App:
First of all, please be sure to confirm the question of who is the master and who is the slave between uni-app and native code.
If the application is developed mainly by uni-app and you just want to package it offline, then you should not use the uni applet SDK but the App offline packaging SDK, refer to. Also note that offline packaging cannot enjoy paid native plug-ins in the plug-in market. If you have relevant requirements, you need to develop your own native plug-ins. Also note that offline packaging cannot enjoy paid native plugins in the plugin market. If you have relevant needs, you need to develop native plugins yourself.
The problem of mixed development of uni-app and native applet:
Use the feature that releases as a mixed subpackage
npm run build:mp-weixin -- --subpackage=sub1or
yarn build:mp-weixin --subpackage=sub1
Third-party developer plugin, Reference
If you want to give full play to the cross-end features of uni-app and compile it to various other small program platforms, it is recommended to use scheme 1.
If you don't need other small program platforms, only need h5 and app, then plan 1 and plan 2 can be used.
If you only need to develop WeChat mini-programs, but want to use Vue to develop, or want to use the plug-in ecology of uni-app, or want to reuse some pages across multiple terminals, then use option 3.