Regarding “how much” in terms of EBTs studies for “the actual path to liberation”, I suggest at least one should study completely and carefully the fundamental or essential teachings of Samyutta-nikaya/Samyukta-agama (SN/SA) (the so-called sutra-anga portion of SA/SN).
See:
Systematic & Structured Approach to Buddhism - Q & A - Discuss & Discover
Choong Mun-keat, The Fundamental Teachings of Early Buddhism: A Comparative Study Based on the Sūtrāṅga portion of the Pāli Saṃyutta-Nikāya and the Chinese Saṃyuktāgama (Series: Beitrage zur Indologie Band 32; Harrassowitz Verlag, Wiesbaden, 2000).
Early Buddhism resources (section 10) Dhamma Wheel