Hi Hyacinthos, Welcome to The Mattress Underground 
Glad to have you here.
First, congratulations on your Residency! As you’ll likely have some long days ahead of you, finding the correct mattress is important. Your ideal mattress is unique to you and is based on your stats (height, BMI, sleeping position(s), and any underlying health conditions,), and your PPP (Posture and alignment, Pressure relief, and Personal preferences). As this is your first mattress; you might want to take a look at themattress shopping tutorialto get an idea of what to look for, and also the mattress specifications you need to know, as well as themattress durability guidelines hereto get an idea of how different types of mattress components will last.
I took a look at the (12") Allswell Luxe Hybrid on their site, and while its’ very inexpensive, remember you ‘get what you pay for’. The bed-in-a-box companies, like other large retailers, are generally not very transparent on their materials or the details of their beds. This mattress has 2 inches of memory foam of unknown composition and density, and 1 inch of HD gel foam, also of unknown properties. I would caution that more than an inch or so of inexpensive memory foam of under 4lbs/cuft and polyurethane foam of less 1.8lbs/cuft will prematurely ‘break down’ which can cause alignment issues and pain (you can see some comments regarding this inpost #7 here)as you say you have neck and shoulder pain occasionally.
Since you ‘sleep hot’ you may want to consider a mattress with a more breathable top layer to get better air circulation and keep perspiration away from your body. While Memory foam is good for minimizing motions transfer, it is generally the least breathable and most insulating of the foam comfort materials, so temperature can be an issue. Especially if you like a soft comfort level then you’d want to make sure that you don’t choose something with too much memory foam on top that you sink in too deeply as the more you sink into it the more will sleep hot. The layers and materials closer to your body will have the most effect on how hot you sleep on any mattress.
It’s difficult to address the sleeping temperature of a mattress for any particular person because there are too many variables involved including the type of mattress protector and the sheets and bedding that you use. Memory foam in the comfort layers and how deep of a cradle this forms around your body would be the main offenders when it comes to sleeping hot. A bit of research on materials like latex, wool, and natural fibers can go a long way You can read more about the many variables that can affect the sleeping temperature of a mattress or sleeping system in post #2 here that can help you choose the types of materials and components that are most likely to keep you in a comfortable temperature range.
Some consumers use a mattress topper made with natural fibers or latex to help with this temperature regulation as well.
I would not make a purchase based on other people’s reviews. While people’s experiences are good indicators of how a company operates and its customer service, reviews won’t tell you much if anything about the suitability, quality, durability, or “value” of a mattress for any particular person (see post #13 here ). I would avoid considering reviews as any sort of a reliable indicator of the appropriateness of any particular product for one’s specific needs. Reviews are also incentivized and given shortly after purchase by consumers who are almost exclusively unqualified to render an educated opinion about the product they have purchased.
You may be lucky and Allswell may be comfortable for you to begin with, but be aware that lower density memory and polyfoams will start breaking down you may end up replacing it within a few years or even months. As I like to remind consumers: ‘caveat Emptor’, let the buyer beware.
As far as other options out there you have not given your budget, nor your personal stats and preferences but you may want to take a look at the offerings of theTrusted membersof the site, who have excellent transparency in materials and components, Many of different options of types of bedding systems, shipping options, and will lend you their many years of experience with a focus on finding a good match for your specific needs and preferences.
I wish you well as you embark on your residency!
Basilio