I think chrome is really ram intensive so using a lighter weight browser may help reduce battery drain (I noticed my Chrome using 1GB system RAM one time). Although I think a lot of the issues may be tied to the websites.
I dunno since switching to Duckduckgo browser I've noticed it takes very little battery at all. Also its only 70 or 80mb max including cache whereas the other major browsers can be 10x as much. I used Edge which I liked too and was linked to my Microsoft 365 too, tried Samsungs One too which also liked a lot but after less than a week both are around 6-700mb in size and hogging battery. They reduce way down when I clear the cache and delete browsing history etc. But I feel you need a normal browser to compliment one like DDG as it's privacy focused implementation can hamper certain things so I use Samsung Internet and DDG depending on what I'm doing.
Not really, there's nothing much in the way of background services used by either browser on the Android platform. If you are concerned that much by battery life then enable lite mode in Google Chrome, install Google Go, Google Maps Go, Gallery Go and disable the full fat versions. That would be a reasonable compromise. You can disable them completely of course and run your device akin to LineageOS which seems to be your desire. Samsung equivalents are all well and good but some lack certain functions. HERE maps by Nokia is a good alternative too. Samsung are not the way ahead long term as they are also cutting back services for cloud storage and have a habit of abandoning apps or confusingly offering multiple versions in their app store of the same thing.
I still have 18GB left of my 19GB Google Storage. I don't tend to upload images that often, the last batch were historical images I'd scanned to share with a School in Germany my Grandmother attended while her Parents worked there too. They are researching the history and asked former pupils to help with any information or photos they had.