Im running a Sketch document with about 40 pages and a total of 600 artboards with no problems on a macbook pro 16gb i7 512gb 13inch 2016 paired with 5k LG 27. Could be even smoother i guess if the sketch document was done properly and divided into different files with libraries etc. It eats alot of ram though if the project is large. 16gb could be useful but my mac mini at home is running the same document even better on only 8gb ram so shouldnt be a problem with 8gb ram as long as you get a better mac than 2016 13inch
Figma and XD is super smooth but haven´t tried large documents.
Photoshop works fine but Im not a heavy user. No retouching just minor tweaks to photos and using it more like a tool with macros.
Vscode depending on how large the project is can be heavy for me with everything above opened. Browsing a large tree and open folders etc feels clunky sometimes. But if you are not like me and are building up an extremely long tab of open files it should be fine (i guess).
I would go with 15 if you can

Otherwise 4core 13inch. 8gb ram should be fine but 16gb is worth the money imo. Skip Macbook Air and go for 2017 non touchbar macbook pro if the 4core is pricey (better screen etc).