Have you built your beds yet?
I think 4X8 is a good size you want to be able to reach the entire bed without stepping in it .
afraid I may not be of much help because of the difference in zones , when it comes to planting and such
my beds happen to be 4X4 so I can more easily move or stack them ,
they are built of poly wood the kind of recycled stuff decking is made from.
my first set were oak rough sawn 1x10 boards but they have rotted away and what i have now are the replacements
I have been gardening here in raised beds for 20+years , I find they have many advantages for the small gardener. For me having a defined space to weed, plant ,and water works best . I rotate crops and use lots of compost .
I have all my cold crops planted cole crops onions salad items ect...
the tomatoes and peppers are on hold in the greenhouse.
What are you planning to grow ? Is this your first garden?