But if we install different applications from play store due to issues in the inbuilt options, think about the RAM management and the battery consumption. I'm worried in that only.
I understand you, but I have to assure you that it's not at all related, it's just about choosing the right applications. You can have system apps that will use more memory and battery than apps installed from the Play Store. Often, the system ones may never get any major updates or advanced configuration options. They will never have as many users as the best-quality applications with a huge user base, where you can also expect more support from developers whose budget by number of users is nowhere else.
Years of experience have taught me to carefully select, stick to, understand, and use the best applications. On each of my phones, albeit from different manufacturers, I am in the familiar environment of my favorite applications.
The apps I value the most, without which I can't be:
Tasker that can replace hundreds of standalone dedicated applications and tools
Nova Prime launcher & Sesame shortcuts & FNG & Tiles
Nearly all Google apps: Play, Pay, Gmail, Phone, Contacts, Clock, Camera, Photos, Keep, Now, Calendar, Maps, ...
AdGuard, AccuBattery, Nine, MiX, X-plorer
I have a total of 178 user applications and have zero issues with memory or battery on the other hand I also disabled some system apps: