Regarding the question, “In particular…is there anything which produces somewhat similarly reliable results with fewer questions?”
You should take a look at the published research on the Usability Metric for User Experience, published by Finstad (2010). The UMUX has four items and has typically been found to have desirable psychometric properties and to have scores that correlate highly with the SUS and, in some studies, have also produced scores that track very closely with SUS scores in magnitude.
In 2013, Lewis, Utesch, and Maher took two of the UMUX items to produce the UMUX-LITE. According to the abstract of that CHI paper, “In this paper we present the UMUX-LITE, a two-item questionnaire based on the Usability Metric for User Experience (UMUX). The UMUX-LITE items are “This system’s capabilities meet my requirements” and “This system is easy to use.” Data from two independent surveys demonstrated adequate psychometric quality of the questionnaire. Estimates of reliability were .82 and .83 – excellent for a two-item instrument. Concurrent validity was also high, with significant correlation with the SUS (.81, .81) and with likelihood-to-recommend (LTR) scores (.74, .73). The scores were sensitive to respondents’ frequency-of-use. UMUX-LITE score means were slightly lower than those for the SUS, but easily adjusted using linear regression to match the SUS scores. Due to its parsimony (two items), reliability, validity, structural basis (usefulness and usability) and, after applying the corrective regression formula, its correspondence to SUS scores, the UMUX-LITE appears to be a promising alternative to the SUS when it is not desirable to use a 10-item instrument.”
There have been additional studies of the UMUX-LITE since then. Here is a list of papers to read on the topic:
Borsci, S., Federici, S., Bacci, S., Gnaldi, M., & Bartolucci, F. (2015). Assessing user satisfaction in the era of user experience: Comparison of the SUS, UMUX and UMUX-LITE as a function of product experience. International Journal of Human-Computer Interaction, 31, 484-495.
Finstad, K. (2010). The usability metric for user experience. Interacting with Computers, 22, 323-327.
Finstad, K. (2013). Response to commentaries on “The Usability Metric for User Experience”. Interacting with Computers, 25, 327-330.
Lewis, J. R. (2013). Critical review of “The Usability Metric for User Experience”. Interacting with Computers, 25, 320-324.
Lewis, J. R., Utesch, B. S., & Maher, D. E. (2013). UMUX-LITE – When there’s no time for the SUS. In Proceedings of CHI 2013 (pp. 2099-2102). Paris, France: Association for Computing Machinery.
Lewis, J. R., Utesch, B. S., & Maher, D. E. (2015). Measuring perceived usability: The SUS, UMUX-LITE, and AltUsability. International Journal of Human-Computer Interaction, 31, 496-505.