Tempo

Look up spoon shaped bags. I have a nemo tempo 20 (which is synthetic) but they have down versions for more money. As a side sleeper it allows enough room to turn over in while also still packing to a compact-ish size.

Really depends where you are, not sure where OP is exactly. Here it can be almost 30°C (86°F) during the day, but drop to around 0°C (32°F) overnight. I use a Nemo Tempo 20 and still need a warm liner sometimes. 

I haven't used these specific bags, but I did have a women's Marmot Trestles bag, rated for 15°F and I always slept very cold, even when temps were just hovering around freezing but not below. I bought a Nemo Tempo, rated for 19°F, and sleep significantly better, even when temps go below freezing. I also love the flap at the top, if it's cold or the sun is coming up and too bright, I pull it over my face and it's nice and cozy. The Marmot definitely feels like good quality, the zipper was really solid, it had a pocket (my Nemo Tempo doesn't), and just felt really nice, but did not keep me warm for some reason. 

I love my Nemo Tempo.  A quilt would probably be better, but they aren't in my budget. 

Which 2 in 1 are you referring to? The ones that come to mind would exceed your budget, but examples help.  What temperature are you expecting at night?  Mainly, I would suggest finding an insulated sleeping pad with a stated R-value. Depending on how cold it will be, the R-value changes (higher R for colder temperatures). For sleeping bag, add at least 10°C, so for example, if you expect overnight temperatures around 5°C, find a bag rated for -5°C.  I have a Nemo Quasar insulated pad in the double width (I move a lot), and a Nemo sleeping bag (in their "spoon" style because I can't sleep in a mummy style bag). 

The forte is my favorite sleeping bag I’ve ever owned. Lots of nice details. Pillow holder, draft stopper, vent sections, phone/light pocket. And the spoon shape makes it so comfortable. I’m sure the tempo has a lot of the same, but the extra weight for 1 degree is definitely not worth it.

Totally get why you’re stuck on this they’re close enough that it’s not an obvious call. From my experience, that 1° rating difference never really showed up for me, but extra weight definitely did once the miles added up. I’ve usually been happier carrying the lighter bag and just throwing on an extra layer if it’s colder than expected. If you’re mostly hiking in, I’d probably lean Forte too, but I don’t think you’d be unhappy either way.

Just be aware of that shoulder girth spec — for the regular version, Tempo has a few more inches and may be a bit more comfortable if you’re a side / active sleeper. If the shoulder spec isn’t a concern the Forte seems like a nice bag at that price. I have an older version of the Tempo and really love Nemo’s spoon shape.

Nemo bags zip together, or at least some of them. I have the tempo and it'll zip with the opposite genders bag.

I like the Nemo sleeping bags that have the gills. You can open them when it's warmer and zip them up as the temperature drops. Works much better for me than just opening the side zipper, which I find let's too much heat out.

I have a cot also but would never sleep on it without a pad when it's cold. I need the insulation. I really like the Nemo spoon shaped bags to be able to move around but why not pile up thick blankets for your first time out before dropping the money on a good bag.