If we have a general online mortgage application that does not distinguish between fixed and variable should arm disclosures be provided ?

IF you allow the applicant to apply for an ARM, you must provide ARM disclosures at the time the application is provided. Comment #5 to §1026.19(b)(2):
v. Form of electronic disclosures provided on or with electronic applications. Creditors must provide the disclosures required by this section (including the brochure) on or with a blank application that is made available to the consumer in electronic form, such as on a creditor's Internet Web site. Creditors have flexibility in satisfying this requirement. There are various methods creditors could use to satisfy the requirement. Whatever method is used, a creditor need not confirm that the consumer has read the disclosures.

I don't think it's okay to promote and accept applications for ARMs but try to say "I didn't know they were going to apply for an ARM." If you make it possible to apply for the ARM, you need to provide the disclosures as required.

Put the online form behind a page that asks one question with two possible responses: fixed interest rate?, adjustable interest rate? If the applicant clicks, checks, or otherwise chooses "adjustable", then detour through online delivery of the time-of-application disclosures before reaching the blank application form.