Well, one challenging part is that the timeline is uncertain. It might be as soon as 3 years or as long as 7. Different savings pathways has different tradeoffs.
For example, in one pathway you initially set more towards retirement and increase the proportion towards the downpayment closer to the time of purchase. This path leads to better retirement savings but the downside is that it reduces the flexibility in timing the purchase.
In the opposite direction you can front load downpayment savings and defer retirement saving. This path has opposite tradeoffs: improved optionality but reduced retirement savings.
I've been struggling lately with how to balance those tradeoffs. In my 20s I knew that a home purchase was so far away because of my career that following the first path was an easy choice. But now that I'm in my 30s and more settled I'm unsure of how aggressively to slow my retirement savings and start saving for a house.
Honestly, for spending and savings accounts I don't think you can beat no-fee online banks. I've checked out local credit unions a couple of times over the years. The fees were always higher (and not much lower than the big 5) and the savings account rates were lower.