Combining reCAPTCHA v2 and v3

I'm keen to use reCAPTCHA v3 for logins and stuff, but I'm unsure what to do with a 'low rating', it doesn't feel safe to deny access with no way for the user to move forward. What feels like a more complete solution would be to combine the "rating" from v3 with a puzzle challenge from v2 if the score is too low. How are other people approaching this issue?

Also, it appears that v3's grecaptcha.execute returns a similar result to v2, that is too say that it's not returning a rating, just a TOKEN which is verified in a similar way to v2?

I've code i found to demonstrate that they can both be used in the same HTML...

<!-- https://github.com/google/recaptcha/issues/279 -->
<script src="https://www.google.com/recaptcha/api.js?onload=v2_onload"></script>
<script src="https://www.google.com/recaptcha/api.js?onload=v3_onload&render=V3_SITE_KEY"></script>
<script src='https://www.google.com/recaptcha/api.js?render=V3_SITE_KEY'></script>
<div class="g-recaptcha" data-size="invisible" data-sitekey="V2_SITE_KEY" data-callback="v2_callback"></div>
<script type="text/javascript">
    function v2_onload() { console.log('v2 loaded'); }
    function v3_onload() { console.log('v3 loaded'); }
    function v2_callback(token) { console.log('v2 token: ' + token); }
    function v3_callback(token, score) { console.log('v3 token: ' + token +    " ----- " + score); }

    // call these manually
    function test_v2() { grecaptcha.execute(); }
    function test_v3() { 
    grecaptcha.execute('V3_SITE_KEY' , {action:'thisIsATest' }).then(v3_callback); 
}

I have concerns then that if v3 requires sever-side validation, in order to implement v2 as well, either a page reload to invoke v2 (when server-side says "low rating" then reload and enable v2) OR v3 sever-side validation could be done via an ajax call, but that feels like something that can be inspected and manipulated by a bot (grab ajax response, change 'no' to 'yes' and then have the bot call the 'callback' function itself to gain access).

Any help or suggestions would be appreciated.