Not sure if I fully understand what you mean, but I think there are two ways.
1. Make a filter that's populated by the podcasts you want to watch, narrow it down by including only unfinished (i.e. partially played) and unplayed episodes, both downloaded and not downloaded episodes, and you can further narrow it down to include only episodes within the last weeks/month. These can be sorted oldest to newest or vice-versa. No manual sorting, as far as I'm aware of. I don't recall if Overcast has this kind of episode filtering, but I really love this feature. I've recently started organizing my podcast feed by genres and play states this way, and it has been a revelatory experience.
2. The 'up next' queue can be configured so that
specific podcasts' episodes are auto-added to it. I haven't made much use of this though, so I can't really attest to how well it works. Unlike the filters, this queue
can be manually sorted (by holding and dragging episodes up/down). However, I think you can only have one such queue.
For what it's worth, I made the switch to Pocket Casts after being a long-time Overcast user and haven't regretted it since. The ads got annoying and it's cheaper to simply buy Pocket Casts than paying the annual fee to get rid of them on Overcast.
