I'm going to answer this question from a non-biological perspective, as I think the question you're actually asking is 'Can a Squid be as intelligent as a human?' The supplementary question being 'Can squids function like humans?' This latter question is a mine-field of broad issues so let's deal with the first question first...
In order to answer this question correctly, it is perhaps first necessary to understand what intelligence actually is. In computer science, the definition for intelligence we use is that intelligence is the ability to identify and recognise patterns of varying levels of complexity and completeness.
That is to say, an intelligent creature is able to see connections between things that an unintelligent creature can't, and can see obvious connections faster. This may seem obvious, but this level of precision is important when you consider how often intelligence is conflated with knowledge, awareness, liveness, consciousness, etc. The important point to note is that intelligence by this admittedly narrow definition means that there are already neural networks that are arguably far more intelligent than humans within a narrow domain (neural networks are basically just complex correlation detectors) but that doesn't make them all that 'useful' as human replacements.
Humans have capabilities that are related to intelligence that computers lack; curiosity, drive, contextual awareness. These are just some. So, is it possible that your cephalopods can be made to be as intelligent as humans? Sure. In point of fact, this is already being looked at given some of their demonstrations in the past.
The next question though is whether or not that intelligence can be harnessed in a way that we would deem useful. Believe it or not, humans have a lot of other body configurations that directly support their intelligence that have little to do with the brain. Arguably the opposable thumb (allowing us to be tool users) has contributed a lot to our ability to build intelligence, as has vocal chords (allowing us to share learnings rather than force all to build from scratch). Some cephalopods have dexterous tentacles which might replace the opposable thumb in some regards, but the lack of language is a much larger barrier.
An intelligent creature with which communication is impossible isn't 'useful' as a member of a social society. Certainly, the body of patterns such creatures can call on is limited to their personal experience. Part of what makes humans so intelligent today is that we're not learning our patterns from scratch - we have oral language that allows us to learn from what people tell us, and more importantly we also have written language that allows us to learn from people throughout history that don't need to be present in our immediate vicinity in order to share their own learnings.
The advent of things like the internet has made knowledge even more accessible and is arguably manifested in what we call the Flynn Effect, which is the drift to higher intelligence over time by humans thanks to more accessible knowledge. Being knowledgeable or having access to knowledge doesn't necessarily make one intelligent, but it does act as fuel for intelligence in the form of raw data from which patterns can be identified.
So; your squid and octopus related human analogue is possible, but regardless of the biological considerations, you need to make your species capable of efficiently sharing information and learnings between them at a greatly accelerated rate, and that generally means a language of some form, even if it is a sign language to begin with.
All this said; the way to think about it is this;
1) The Biological structures define the upper bound of how intelligent your creature can be. The neural structures have to be able to process sensory input and integrate it with the existing body of knowledge in real time, and the more that can be done, the more intelligence is possible in your chosen creature.
2) The Environment will define how much of that intelligence will be realised. Part of that may be biological, like the opposable thumb, but ultimately your environment needs to provide a rapid and efficient delivery of existing knowledge on which your intelligent creature can build, laying down learnings on that foundation for the next generation to utilise in their own turn.
If you provide for both of those things, then your cephalopods have a chance at realising the massive potential you are setting for them.