[double00]

On my layout using 00 Peco railtrack, that includes point work, my rolling stock is a mixture of HO and 00 scale that gives no trouble what so ever. I have found that H0 though much more expensive to buy, the product is much more reliable to run and materials better quality. I have two diesel locomotives manufactured by Fleischmann in the 1980s, that today, runs as efficently as when bought new. Most of my other rolling stock made by various manufacturers do couple up to the H0 locomotives without any trouble.
I must admit that I am not a perfectionist for details, rather enjoy to watch the rolling stock run on the layout - enjoyment is my number one.

 

[double00]

You mention that all 00 coaches will not fit H0 locomotive couplings.
I have a mixture of both H0 and 00 locomotives, coaches and I am able to couple an HO coach to a 00 locomotive and vice versa.

 

[double00]

I must admit that I run my railway models simply for enjoyment and have no thought in accuracy to scale, except everything is 00 or H0 gauge. My layout looks good, well to me anyway and I have no wish to exhibiting it in public.

 

[double00]

Both gauges 00 and H0 locomotives, coaches and wagons can run over the same gauge of either 00 or H0 track, therefor inter changeable.
As it was pointed out in another forum, that the new couplings can cause problems when coupling up the different rolling stock gauges if fitted with older type couplings.
I did find the Fleischman DMU 614 two car set, has the new couplings fitted and making it impossible to interchange with my other models. At present I can use the 00 and H0 on my gauge 00 layout.