How would it be better for absorption? ...

Remember, pharmacokinetics are infinitely more complex than most people realize. The absorption pathways and chemical/physical interactions all play a role in the specifics of how well things absorb alone or in combination. Some things absorb through pathways that have a lot of bandwidth, while others fight for more limited pathways. The β-glucans in mushroom are considered soluble fibers. Even different types of β-glucans act differently. β-Glucans having β-(1→3) linkages and high degree of polymerization are completely insoluble in water. The viscosity of β-glucan in the gut is mainly responsible for its cholesterol-lowering effects. That viscosity is directly related to its molecular weight and solubility in water. High molecular weight and high solubility in water of β-glucans have high capacity of reducing serum cholesterol compared to low molecular weight and low soluble β-glucans. β-Glucans that have high molecular weights form viscous and pseudoplastic solutions, whereas β-glucan with low molecular weight forms softer gel at high concentrations. β-1,3-Glucan molecules are pretty much resistant to the acid in the stomach. After ingestion, β-glucans gradually passes into the first section of small intestine and are trapped by macrophage receptors located on intestinal wall. When glucan molecules comes in a contact with glucan receptors, they are activated and generate bactericidal compounds, such as lysozyme, reactive oxygen radicals, and oxides. After that, cells commence to yield numerous cytokines, which activate the surrounding phagocytes and leukocytes that lead to specific immunity. This is how many of the β-glucans improve immune response. It's all happening in the GI tract, and part of the effects are through the gut-brain-axis.

Then you have the other compounds, like the triterpenes in reishi or diterpenes in lion's mane, that absorb through different pathways and interact centrally. The different compounds follow different pathways than each other, too. So a triterpene in resihi would absorb through a different pathway than a diterpene in lion's mane. We are still elucidating all the specifics, though. It's hard to make wide sweeping statements on things, because the specifics are complex and still being studied. Be careful to avoid blogs discussing all this, as most are full of bullshit. So many blogs out there make massively oversimplified statements that are not based in scientific fact. It's true that many elemental forms of minerals and metals compete with each other for absorption. So spreading out those is a good idea, or taking them in forms that don't pose that risk. So taking magnesium at a different time than calcium is a good idea. However, be careful not to apply that to other things willy-nilly. Our Microzinc is going to absorb through a different pathway than zinc oxide, which would absorb differently than a chelated form of zinc. If we paint things with too wide a brush, we lose sight of the specifics that matter.

Regarding your specific question, I would just space out the mushrooms from each other throughout the day to avoid GI upset. Taking 6 grams of a mushroom extract at once is a sure fire way to upset your stomach. Remember, they are full of both soluble and insoluble fibers. So limiting the amount you take a once is a good idea. I like to keep my mushroom doses to 3-4 grams or less per dose at the max. I would probably take the shiitake and maitake in the AM, and the reishi in the PM. Reishi is calming, so that is better at night. Shiitake and maitake both have compounds in them that affect AMPA, so they can be stimulating. Keep those for the morning.