You are not likely to be happy. TurboTax Online does not have forms mode. There is no way to make entries directly on the forms. The CD/Download software also has other features and capabilities that are lacking in TurboTax Online. It is a far superior product. If you're happy with the download software, stick with it.
Also note that there are a few uncommon entries that are not covered in the interview and can only be made in forms mode. If you happen to need one of those entries, you can't do it in TurboTax Online at all.
The online version is different. There is no Forms Mode. You have to use the interview entry method. You can't see the forms until you pay. Online is only good for 1 return per account. And you may need to upgrade to a higher version to enter something.
If you used the Desktop program before you may not like the online version. It has less features and no Forms Mode. You can only do 1 return. Your return is only saved online so be sure to save both the .tax2020 data file and the pdf file to your computer when you are done. In case you need to amend in the future or if you need a copy to get a loan or something. You might not be able to access your online return when you need a copy.
FYI ... although they try to upsell you at every turn ALL the downloaded versions can handle ALL the same forms ... the only difference is a little more "hand holding" in the upper versions. So you can use the Deluxe if you need a state program and the Basic if you don't. If you shop around and wait until at least February you can find a better price outside of Turbotax direct.