Is it true that Google Search can’t read more than 70 characters of a webpage title?
From the google SEO guidelines (Google Search Engine Optimization Starter Guide - Page 4):
Use brief, but descriptive titles Titles can be both short and informative. If the title is too long, Google will show only a portion of it in the search result.
- using extremely lengthy titles that are unhelpful to users
- stuffing unneeded keywords in your title tags
As outlined, titles should not be too long - eventually make use of the "description" meta tag (Google Search Engine Optimization Starter Guide - Page 6)
Description meta tags are important because Google might use them as snippets for your pages.
To answer the question: to me this is obvious - titles should be as short as possible - for a detailed description the description meta tag should be applied. For your specific question - there is no direct answer - as im aware <55 chars is perfect, ~65 chars are reasonable but still a lot, 75 absolute maximum and should be avoided.