I’ve travelled throughout Japan many times, so I am no stranger to the types of accommodations one will encounter during their stay.
If you’re a solitary traveller planning to spend your days exploring Tokyo, this location will serve well as a functional home base. It’s smaller than it seems in the photos - but that’s very normal in Tokyo. Thing is, the size isn’t an issue for a single traveller, as you’re going to be too busy out and about anyway! Just note that function overrules everything else in this situation - it’s a place to peacefully sleep, shower and store your luggage.
And that’s where this place excels - location. Shinjuku station will no doubt serve as a central hub in your travels & being in a very quiet & peaceful neighbourhood near the train station makes a big difference.
Also, it seems like units with pocket wifi (and must for travellers) have become more & more rare, so the fact that this unit has an excellent pocket wifi is another big plus.
A nice stay!