I only keep planted tanks so I don't really know if more flow is beneficial for non planted or not. However, most of use want to over filter, and have a lot of flow.
I would recommend bigger. I would do a 2213 on the 8 gallon but a 2211 would be fine. I would recommend a 2217 on the 36. So, my opinion obviously is they are by no means overpowering, and would be underpowered for my taste.