If we start from the fact that every human is different and has different feet with hundreds of variables and you can start to see the size of the problem.
Unless you are prepared to spend the thick end of £2000 on a pair of custom made and fitted boots every boot choice you make is a compromise on the best fit for your particular feet.
The market place for boots is extremely competitive and the vast majority of manufacturers now build to a price point for the mass market and closely mirror each other like sheep. Most manufacturers are only interested in high volume sales and making the most profit per pair that they can get away with. Making and selling a quality product is now well down the list of priorities for the majority of them. Unfortunately these days a budget of £100 buys you very little in the way of a quality product. The trend towards manufacturers reducing the quality of the materials used to increase profits and building in a short lifespan are other worrying aspects to this.
Perhaps the only exception to this is Altberg who offer what is probably the widest range of models in different width fitting and last shape combinations available. This individuality obviously comes at a cost which some people are and some people aren't prepared to accept and pay. Add to this the time and cost of either a visit to the Altberg factory or a specialist boot fitter such as Whalley Warm & Dry and you can see it's not a cheap undertaking if you want the best possible fitting boots for your feet without going to the expense of custom made boots.
The Altberg boots broadly fall into 3 categories depending on your walking requirements.
2-3 Season Boots -
Fremington (standard last with 5 width fittings),
Yan Tan (A-Forme last with 1 width fitting),
Malham (A-Forme last with 1 width fitting),
Keld (G-Fit last with 1 width fitting with a much higher than average volume & width)
3 Season Boots -
Tethera (standard last with 5 width fittings),
Nordkapp (A-Forme last with 1 width fitting),
Kisdon (G-Fit last with 1 width fitting with a much higher than average volume & width)
3-4 Season Boots -
Mallerstang (standard last with 5 width fittings)
If the standard last doesn't quite fit the shape and volume of your foot it's a safe bet that either the A-Forme or G-Fit lasts will and you will definitely not be disappointed with the build quality of any of them.
A couple of links which may be worth reading
https://www.myoutdoors.co.uk/index.php?option=com_k2&view=item&id=976:alt-berg&Itemid=279https://www.altberg.co.uk/a-forme/the-history-of-a-forme/