The Greek word πᾶς, πᾶσα, πᾶν, πάντα must be defined with great care so as not to make it say more than was intended. BDAG defines five different meanings for this word:
- pertaining to totality with focus on its individual components, each, every, any. eg, Matt 3:10, Luke 3:9, Matt 15:13, Luke 3:5, etc
- any entity out of a totality, each and every, every, eg, 1 John 4:1, Eph 4:14, Matt 18:19, 12:31, 2 Cor 1:4b, etc
- marker of the highest degree of something, all, eg, Acts 4:29, 5:23, 23:1, etc
- pertaining to a high degree of completeness or wholeness, whole, eg, Matt 2:3, Rom 11:26, Acts 2:36, etc.
- everything belonging, in kind, to the class designated by the noun, every kind of, all sorts of, eg, Matt 4:23, 23:27, 28:18, Acts 2:5, 1 Cor 1:5, 6:18, 2 Cor 7:1, etc.
Let us now examine the two examples highlighted by the OP.
Mark 10:27 - Jesus looked at them and said, “With man this is impossible, but not with God. For all [things] are possible with
God.”
In this instance, the word "things" is supplied by the translator. However, the meaning of πάντα here fits into #5 above, namely "all things in an implied class of things". The implied class of "things" here is all the things that God does in His sovereign providence. [This obviously does exclude some things because God is not the author of sin!]
Matt 19:26 - And Jesus having looked on them, said to them, "With men this is impossible, but with God all [things] are possible."
Same comments as above.