BEM mixin two elements into the single Dom

Question

Hi'm confused BEM methodology. Can I mixin two elements in dom node? i.e.

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    <p  class="txt__large txt__bold">...</p>
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or

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<p class="text__large wrapper__header>...</p>

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And can I use mixin modifier and modifier value i.e.

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<p class="txt txt_small txt_small_colorized>...</p>
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Is block correct according to BEM? So Can I use txt block elements or container-1 elements in header?

<header class="container-1 txt">
      <p class="txt__xlarge">something</p>
      <p class="txt__xlarge txt__xlarge_color">something/p>
  </header>