Enclosed

In the past I wrote like no. 1 because it is typical pattern of business letter.

Few years ago I started changing to no. 2 because the global has moved towards writing in Plain English - the modern business writing style that emphasizes on using clear and direct English.

So if the receiver is in traditional style, take no. 1.
If the receiver is in modern style, take no. 2.

All 1, 2 & 3 are good but are slightly different in certain manners.
I would say:
2. Good
1. better
3. best
I suggest it's even better if you put it like this:
Please find the enclosed Schedule A and B for your kind reference.

The first one is the best, because it is gramatically correct, and it is also very polite.
The second one is gramatically correct.
The arrangement for the third one seems a bit strange.

I think that 2 is the best. It's concise and grammatical. I find 3 acceptable, but not 1.