What form should I keep my tax records in?

The IRS has a web page that explains this. You can also google for "How long should I keep tax records" for other explanations. Since the powers that be like a synopsis, below are the highlights:

https://www.irs.gov/businesses/small-businesses-self-employed/how-long-should-i-keep-records

Period of Limitations that apply to income tax returns

• Keep records for 3 years if situations (4), (5), and (6) below do not apply to you.
• Keep records for 3 years from the date you filed your original return or 2 years from the date you paid the tax, whichever is later, if you file a claim for credit or refund after you file your return.
• Keep records for 7 years if you file a claim for a loss from worthless securities or bad debt deduction.
• Keep records for 6 years if you do not report income that you should report, and it is more than 25% of the gross income shown on your return.
• Keep records indefinitely if you do not file a return.
• Keep records indefinitely if you file a fraudulent return.
• Keep employment tax records for at least 4 years after the date that the tax becomes due or is paid, whichever is later.

FWIW, for decades I have been keeping my returns for 7 years.

Revenue Proclamation 97–22 is what specifies all the rules for storing your tax documents electronically (to keep them in a format that would be accepted for audit): https://www.irs.gov/pub/irs-tege/rp-97-22.pdf

In short, yes this is fine but comes with a few additional requirements over that which you would have to follow if keeping originals. Section 4 of the documents covers them all but in brief the most important ones are:

• An electronic storage system must ensure an accurate and complete transfer of the hardcopy or computerized books and records to an electronic storage media. The electronic storage system must also index, store, preserve, retrieve, and reproduce the electronically stored books and records.
• the ability to reproduce legible and readable hardcopies (within the meaning of section 4.01(3) of this revenue procedure) of electronically stored books and records.
• All books and records reproduced by the electronic storage system must exhibit a high degree of legibility and readability when displayed on a video display terminal and when reproduced in hardcopy...
• For purposes of this revenue procedure, an ‘‘indexing system’’ is a system that permits the identification and retrieval for viewing or reproducing of relevant books and records maintained in an electronic storage system.

Basically, you have to be able to ensure the records do not get damaged so are well backed up etc, that you can find and retrieve the correct ones on request, and that you can print good quality hard copies of any record. You must also be able to simply explain how your system works and how you make sure you have and can retrieve all important records the IRS may need on request.

There are some other more obscure requirements so check the document I linked above to see them all. Also check that your state tax office permits use of electronic records.

Other than that, I have been doing something similar to this for years and have never had an issue, though I do use OCR software on the scans to make them more easily searchable, or in the case of documents I have a digital original store that so it is searchable.

TLDR

Go ahead, just make sure you follow IRS requirements.