Open rates are quite subjective. Starting with SPF/DKIM (and to a lesser degree, DMARC) you will want to ensure that they are setup specifically for use with Infusionsoft. This amounts to emails getting delivered in the first place. Open rates are strongly affected by the email clients the emails are sent to. Each has different criteria for reporting opens and some will report opens that have never been opened.
CTR’s, on the other hand, are very reliable, as they depend on an actual person interacting with a link. You will find that content is the greatest contributor to this as content is what motivates the action.
So there are really two subjects here. First is deliverability, which involves getting your foot in the door in the first place. The second is inbox placement, which has more to do with getting the email to the inbox rather than the junk/spam folder and then using content to motivate the desired response.