This is my first review so it may be a little bit messy
Price
The first thing you'll notice is that the locomotive is priced at around 18.95€ or 22 dollars. It is a little bit less than the average price of an average JT Advanced locomotive, which is usually priced at 20€, or 24 dollars. This is definitely a plus. So I'd say, for what you get, the price is relatively justified I guess.
Variety
The locomotive comes in 6 playable variants: 70000 and 70000 with white roof, 70013, BR green clean, BR green weathered and BR green heavily weathered. For all of them (except the two preserved variants) you get a variety of 3 different tenders (BR1, BR1A and BR1D) with BR early and BR late decals. They all come in clean, weathered and heavily weathered. Upon looking into the files of the locomotive I saw a black texture set for the 7mt, so if you are familiar with file structuring and replacing you can easily make a black reskin of the locomotive without having to repaint anything. So I'd say that there's a pretty decent amount of variety.
Simulation
the locomotive is an advanced locomotive, so it is a challenge to drive. It is simulated very well, the ejectors actually affect the brakes (atleast in advanced mode, but I'll talk about that later), the water gauges work, almost every cab surface is interactable and there are onboard electronics on 70000 and 70013. You can switch between advanced mode and simple mode via a switcher program that you can build with a batch file that is located in the locomotive's folder. Just click the batch, and the switcher is built. Run the switcher and you can select the mode. It doesn't always work, so you may have to restart your computer after you ran the switcher for it to take effect. I have noticed one or two negative things: 1. The boiler pressure drops quickly. This is not very good on gradients, as you will use all of the pressure and then have to stop to regain pressure. When standing still, the pressure rises rather quickly though. 2. It is pretty weak, which means it can't really haul more than 4 cars successfully on a medium gradient, making it almost useless for hilly terrain.
Sounds
The sounds are pretty good, the whistle is really cool, but I replaced it with a cool dynamic whistle as that fits a glorious 4-6-2 pacific better. the chuff sounds are pretty cool, but one thing I have noticed that the sounds get louder the further you move away from it. It is kinda annoying to me, but I can cope with it. The safety valves are really loud, but that can be fixed. Overall, it has really nice sounds.
Overall
The 7mt Britannia is my loco of choice. Even though it is not made for mountainious terrain, I still put it infront of up to 12 cars and just pack like a Class 57 or 66 behind and drive it on the West Highland Wandering route. Overall, I'd give it a score of 9/10, as it has amazing details, nice textures, really good variety and good sounds. What not to like? Definitely recommended.