My above example uses rounded values, close to the mass of many heavier cast metal H0/00 models. For my Locomotive fleet of 2-6-0's mass is about 240g,
2-8-0's are around 270g and my 4-8-2 is over 400g. The above example clearly shows a 300g locomotive without a sprung bogie can have a higher tractive effort compared to a 400g locomotive with a sprung bogie. I don't need the extra mass, however if you do, the centre of gravity can be close to the leading driving wheel. For some of my models the centre of gravity about 5mm from the leading driving wheel. The other option is to build the locomotives tender so it adds weight to the locomotive by having a fixed coupling beam and the front wheels of the tender not taking any of the tenders weight.Most if not all of my leading bogies are less than 10g in mass. They all stay on the track at scale speeds, on my layout and they have visited other layouts which used RTR turnouts.
Bearing area has little to do with our model bearings friction. It has allot to do with wear. Friction force = Cofficent of friction x The force perpendicular to the surface. A common emprical formula which has been used for a long time by engineers. I am sure the science was done over 100 years ago to support the formula. That'a a direct proportional relationship.
Inside bearings have a larger drag compared to pinpoint bearings because the friction force acts at a larger radius, resulting in less mechanical advantage.
Minimal compared to the large drag from the sprung bogie in my example using scaled down proportion prototype axle loads.
The total mass on the drivers is what counts. As long as the centre of gravity is between the driving wheels, within reason there is no problem.
You are still ignoring the facts about the increased drag from inside bearings. The end result is less tractive effort as the above examples show.
Using my web page table and my wagon mass formula of 0.58g/mm a 1000 ton train is equal to 13.3 75 ton coal wagons. Wagon length is about 130mm, train length is 1729mm. Train mass is 1003g. To move this train on flat straight track requires a locomotive of only 100.3g mass. My white metal NSW 18 can do it easily. My 0-6-0 whitemetal NSW 18 will move 60 4 wheel wagons without much trouble. A small amount of wheel slip on starting could be observed. It's mass is about 200g. I included a few bogie wagons to get the full equivalent length. Train weight was not calculated. The test includes going through 1 turnout and part of the train was on a slight up hill grade around 1 in 100. It also pushed the train without any trouble. In theory using the table on my web page it should be able to pull a train of at least 2kg. How much mass is in your models will determine how many wagons it equals.
The above experiment proves I can pull full prototype length trains appropriate to the locomotive if prototype curves and grades are used. I have compensated for the grades on mainline curves thus maintaining full prototype mainline loads. My limit is the siding lengths on my layout. If I can do it, so can you.