The 5K window unit does not keep the pop up comfy in the heat of the day. We use a fan with it and upgraded to an oscillating floor stand fan which helped, but still can't stay there during the day in the summer.
I'll keep my eye on the portable 12K unit at Costco.
Our 9,000 BTU portable cooled about the same as a 5,000 BTU window unit in our popup. It doesn't seem like the portables are as efficient in cooling as the window unit in our experience- same thing when the power went out and we used the window unit and portable with a generator in our room.
Don't get me wrong, it's much, MUCH better than nothing and when the heat index was 110- with the portable on high, awning up, shady lot, reflectix on the bunks ends and in the zips, it was a nice dry 76-78 in the popup. The reflectix makes a huge difference, much more so than the popup gizmos we tried when we got the hybrid.
After we got the bunk house rv, we decided to keep renovating/restoring the popup and cut through the box and installed a 8k btu window unit with oscillating fan in front of it. HUGE difference! Even with the triple digit heat indices, we set the unit on 72 and it stayed a consistent 72 throughout the camper.But without the reflectix and binder clips on the bunk ends though...the unit really struggled to keep up and the bunk ends were still really warm. Extra bonus- Reflectix keeps the bright sun from waking us up at the crack of dawn!
We also replaced our old ceiling lights by the bunk ends with the ones that have the power ports on them so we could use the clip on bunk end fan/lights.
You may have already tried all of those ideas though, just thought maybe something we did might help