Since u need to run bootcamp, 128gb is totally out of questions.
256gb is the ‘bare’ minimum but u are likely to rely a lot on cloud storage or external storage still. If u are on Budget constraint, this is the bare minimum that u can go for.
best option should be 512gb which will give u enough ‘working space’ for long run. my ‘working space’ refers to the storage size that can allow u to work on daily basis without regularly move ur files to external storage or cloud storage and enjoy the maximum data transfer rate of the built-in ssd of macbook.
I always see people asking for advices here for storage options, whether 128gb or 256gb enough. When they are advised for going for higher, they will find all sort of ‘reasons’ to ‘justify’ why they can survive with the Low storage option. Some of the reasons they gave will be they can work on cloud storage, they can buy external hardisks etc. Seriously, if u need to find so many ‘reasons’ to convince itself that the Low option can work, it already means that the storage option does not fit u but u just find ‘reasons’ to justify for ur Budget.
Some of them after less than a year, want to find replacement ssd for bigger storage, end up they actually spent more money due to the labour costs, harder to find parts, even can find the storage speed is way way behind the Apple ssd also.
I always believe the theory of “buy cheap and pay twice”. I understand that some may really have Budget constraints, but if that’s the case, u might end up better to go with cheaper options instead of Apple which u can get cheap and big.
Buying something right at the start is important for Apple products since they are not upgradable. Do be warned that new macbook 2019 has soldered storage. Even u want to upgrade the ssd next time, u cannot do so even. Think carefully before u proceed.
Soldered SSD will be greater pain to swallow if wan to upgrade...
With current MBA, i've away got restricted with "low storage" message many times while download things...