This page is aimed to describe best way how to use and utilize this newGRF, including information like which settings or other newGRFs are recommended to be added alongside of NUTS.
It is also noteworthy that NUTS Unrealistic Train Set is completely untested with AIs and they are not supported at all.

openttd.cfg settings

NUTS works as a two-in-one NewGRF. You can use it in both 8bpp, and 32bpp mode. To do this, you just need to specify your blitter in your config file.

blitter = "32bpp-optimized" 

or
blitter = "8bpp-optimized" 

If the setting is empty, it means default - which is 32bpp. In that case OpenTTD will just use 32bpp sprites IF they are supplied by the NewGRF, if not, then it will use 8bpp.

If you put there 8bpp, it will FORCE all newGRFs to use their 8bpp sprites.

That way you can always return back to the original NUTS 8bpp pixel art, or use the new 32bpp/ExtraZoom graphics. :)

Settings

Train acceleration model - realistic

Without a question, realistic acceleration model should be standard in general, but of course as it is one of the options which affects a train set it is fitting to note it.

Breakdowns - off

As OpenTTD is a game about details on the network and NUTS is trying to extend the detailed view on the game, it makes absolutely no sense to play with breakdowns turned on.

Weight multiplier - 1

Since all of the train stats are carefully picked, increasing the weight multiplier anywhere higher than 1 is completely counterproductive as it makes all weaker (Fast) trains completely useless when full.

Hill steepness - 4%

This setting is always very interesting and I generally like using even higher values, but most of the time I use 4% with which NUTS is being tested. I can however see higher setting values being very sensible.

Vehicles never expire - CAN be OFF

NUTS is fully prepared for expiring vehicles. During the game old models will expire, and by the end of the game you will only be able to buy the latest models of each class. Some exceptional trains never expire even if they are not the top of their class.

Servicing - 5 days

Due to new trains coming relatively often and the generally very liberal view on autoreplacing, it can happen that you may need to autoreplace trains often. I personally recommend to set the servicing interval for trains to days (off in percents) and setting the servicing interval value to 5 days. This makes sure that your trains will want to service just when you tell them to (given that 5 days passed since last autoreplace, but that is very short time in the game). This setting only applies to trains constructed in future, not already built trains. It also is a setting only for your client, not for the server.
Note: this expects you have breakdowns set to none

Other newGRFs

NUTS is on one hand kind of unfriendly when you look at adding a train set to it, but on the other hand no matter what other newGRF do you add, be it industry set or anything else, NUTS not only just work but it usually also directly supports it.

Industry sets

Thanks to the universal wagons, NUTS supports literally all cargoes. It however not only supports them, it even has unique sprites drawn for every cargo currently known in FIRS, Pikka's basic industries, or ECS.
My favourite set to add is actually OpenGFX+ industries due to it's perfect playability (same as original industries) while it still adds a lot of variety to the game, not to mention all the various colours of wagons that NUTS provides.
Second is definitely FIRS, which then uses almost all available sprites in NUTS. PBI and ECS are supported but I personally do not recommend those as their playability is very questionable.

Train sets

As NUTS attachment rules are very strict, the engines of the set will always remain unaffected no matter which set you add. The added trains will either be useless as their stats are worse than NUTS, or they will be overly strong and NUTS will be useless. In the second case you would at least gain NUTS wagons which could be reasonable if you were aiming for industry set support.
Logic engine is nice to add if you need to attach wagons to the logic engine.

Infrastructure sets

There are many interesting newGRFs which influence rails and related infrastructure, but some of them are especially fancy to use alongisde of NUTS.
Bridges are definitely the newGRF with most influence to train behaviour, mainly with speed limits of bridges. It is always nice but not necessary to add some bridge set mainly because they have higher speed limits of 3-tile bridges, as the original 256km/h bridges can be annoying.
First of these are newbridges (in openttdcoop grf pack), not only because they include many sorts of brilliant bridges but mainly because they add the pipe monorail bridges which I absolutely love to use.
The other main bridge set there is, Total Bridge Renewal Set. This set is the option to use mainly on servers which use online content only. Still, these bridges are very nice.

Other newGRFs are nice, but usually just eyecandy and do not have that much of a functional value to NUTS therefore do not need to be mentioned here.