We don't know grade, whether you had lymphovascular invasion, size or other factors so hard to "advise."

I had Ontotype of 8, grade 3, LVI. I was told that one in 5 radio-oncologists would recommend radiation. I opted to take Femara (letrozole) but did not do radiation. But that's me.

I already had had osteoporosis when I went on Femara and my doc did not want to do Reclast (due to my afib, but that issue has since been resolved). I lost more bone the first year, but then the bone loss eased- similar to what happened with menopause.

You can take Prolia or a biphosphonate during treatment, if the bones become an issue. I am now on Tymlos and regaining my bone density, I hope.

There is so much fear about aromatase inhibitors. I have to confess I was eager to take them and miss the feeling of safety!

I opted out of site-specific radiation (5 sessions over 10 days). I had an OncotypeDX 'risk of recurrence' score of 3% so no chemo was recommended. I tried an aromotase inhibitor, twice, with resulting side effects that were, for me, not tolerable for such a low recurrence risk.

If the number 16 you cite is your OncotypeDX 'risk of recurrence' number (not the trade-marked Recurrence Score on your report), you can roughly calculate your predicted risk of recurrence as around 30% if you do NOT take aromatase inhibitors or tamoxifen according to the OncotypeDX algorithm. I would consider that a high enough risk that I would at least try the aromatase inhibitors and get an endocrinologist or rheumatologist to help monitor osteoporosis.
It's a personal decision that a lot of us are faced with so you might also get a second oncologist to opine. There may be something that she/he sees in clinical evaluation to suggest a prognosis based on real-world oncology experience.

I would likely at least seriously consider the short-course radiation. Nothing is risk-free but I've known people who've had it without side effects or complications. But that too would be something I'd get a second opinion about.