If you're solely focusing on the English language, no, you shouldn't use CV-C. Any reclist that combines multiple languages, and especially while also claiming efficiency, are doing so at the cost of precision. Phonemes that are written the same way across multiple languages are not necessarily pronounced the same way. The result will be inaccurate "accented" pronunciation across all languages. Shorter reclists also cut corners in the recording process by making the resulting voicebank more confusing and difficult to use.
There are three standards for English-only voicebanks: Delta, VCCV, and Arpasing.
Delta's reclist is based on X-SAMPA, a phoneme system that corresponds directly to the standard International Phonetic Alphabet and will be more familiar to Vocaloid users. It was written for Japanese UTAU users, but English-speaking UTAU users will also get good results.
Reclist:
https://ch.nicovideo.jp/delta_kimigatame/blomaga/ar761052
How to OTO:
https://ch.nicovideo.jp/delta_kimigatame/blomaga/ar761114
Using voicebanks:
https://ch.nicovideo.jp/delta_kimigatame/blomaga/ar764836
PaintedCZ's VCCV reclist is the most popular for English voicebanks on this side of the community. There's a full series of video tutorials. Please click through to the YouTube page so that you can find all the important links in the description.
Arpasing is based on Arpabet and cmudict, which are both frequently used in speech synthesis and many other English-language singing synthesizers. The default reclist is very short, though other users have created longer reclists with more complete coverage of phoneme combinations. There are tools for automatically OTOing the voicebank and automatically converting USTs. Everything you need can be found at the Arpasing website.
https://arpasing.neocities.org/
Other reclists also exist, and you're always free to write your own. As you gain more experience using UTAU, you'll probably find yourself wishing for certain advanced features that aren't already included in the most common reclists, and that's where you can start to customize your voicebanks to fit your own taste.